The Nile River Valley 3.

1
Though the verdant green course of the Nile Valley appears to be the very
antithesis of the bleached Saharan sands through which it flows, these two
contrasting features have together constituted a primary force in the
development of agriculture and settled human society in Africa. The Sahara
acted as a pump, drawing people from surrounding regions into its watered
environments during the good times and driving them out again as conditions
deteriorated (though not necessarily returning them to their point of origin).
The Nile, for its part, was a refuge for people retreating from the desert and
then a reservoir from which the desert region was repopulated as conditions
improved.
1.Which of the sentences below best expresses the essential information in the
highlighted sentence in the passage? Incorrect choices change the meaning in
important ways or leave out essential information.
A The development of settled societies and agriculture in Africa was heavily influenced by
the combination of two physically contrasting areas, the green Nile Valley and the
surrounding Sahara desert.
B The green Nile Valley contributed more significantly to the development of agriculture
and settled societies than the bleached Sahara desert did.
C Agriculture and settled societies were able to develop in the valley created by the Nile
River, even though it cuts through the bleached sands of the Sahara desert.
D Although the Nile Valley appears completely different from the Sahara, the similarities
that existed between these two regions led to the settlement and agricultural
development of Africa.
The Nile is commonly believed to have been a conduit along which the
principles of food-crop cultivation moved from Egypt into more southern
regions of Africa along with the wheat, barley, peas, and lentils initially
domesticated some 9,000 years ago in Southwest Asia. It is true that the
ancient Egyptian civilizations founded on the Nile over 5,000 years ago were
sustained by the exceptional productivity of those crops, but they were a
comparatively recent introduction, arriving long after the cultivation of
indigenous African plants had begun farther south.
2.Paragraph 2 supports the idea that the cultivation of food crops in Africa began
A in the Nile Valley
B long before food crops were domesticated in Southwest Asia
C with the arrival of domesticated wheat, barley, peas, and lentils from Southwest Asia
D with the domestication of indigenous African plants
Contrary to expectations, the earliest evidence of a shift toward a critical
dependence on food production as opposed to food gathering comes not from
the floodplain of the Nile but from sites in what is now the empty and
waterless Sahara. The development was complex, involving the
domestication of plants and livestock, technological innovation, the
establishment of villages, and an increasing level of social interdependence.
3.According to paragraph 3, what is true about the shift from food gathering to
crop cultivation?
A It probably occurred during a period in which the Sahara was becoming drier.
B It probably occurred much earlier in the Nile Valley than people once believed.
C It probably occurred after the establishment of villages along the Nile.
D It probably occurred first in the Sahara and only later along the Nile
The Sahara Desert had been widely inhabited until the last glacial maximum,
when conditions of increasing aridity drove people (and practically all animals)
out of its previously productive wooded grassland and savanna environments.
Essentially nomadic—though exhibiting a tendency to settle at lakesides and
other sources of food and water —the groups moving to the north and south
continued to follow their established hunting and gathering way of life. The
groups that moved east into the Nile Valley, however, adopted a distinctly
sedentary lifestyle. Indeed, they had no choice. The narrow strips of green
floodplain flanking the Nile were bounded by waterless desert and movement
along the riverside plains was restricted by the presence of competing groups.
4.According to paragraph 4, what was true about the Sahara during the period
before the last glacial maximum
A It was almost completely covered with trees.
B It contained few sources of water.
C It contained no large animals.
D It was home to many hunter-gatherers.
5.Why does the author inform readers that the floodplains of the Nile were
"bounded by waterless desert" and that movement along these riverside plains
"was restricted"?
A To argue that the Nile Valley was as affected by increased aridity as the Sahara
B To help explain why some groups became sedentary
C To explain why nomadic groups tended to camp at lakesides
D To explain why some groups moved north and south rather than east
The Nile along which people congregated 18,000 years ago was a quite
different river from that which flows through Egypt today. It was much smaller
and flowed more slowly through a tangle of braided channels across a wide
elevated floodplain rather than along a single massive stream. The river
carried a heavy sediment load, and the silts deposited along its length steadily
raised the level of the river and its floodplain.
6.The word "congregated" in the passage is closest in meaning to
A traveled
B survived
C gathered
D farmed
7.According to paragraph 5, each of the following describes the Nile of 18,000
years ago EXCEPT:
A It was not as large as today's Nile
B It flowed more slowly than today's Nile.
C It flowed through a single stream.
D It contained a great deal of silt and other sediments.
In effect, the Nile Valley at that time was an elongated oasis: a sharply defined
area of inhabitable territory beyond the boundaries of which human survival
was impossible. The oasis extended all the way from the Sudan to what is
now Cairo—a distance of over 800 kilometers—but it was nowhere more than
a few kilometers wide. Its food resources were varied and nutritious.
Quantities and availability, however, were always subject to seasonal variation
and the vagaries of the Nile's annual flood. During the critical two to four
weeks when the flood was at its height each year, people and animals were
driven out of the Nile Valley and crowded into the narrow band of inhabitable
land that lay between the floodwaters and the arid desert beyond.

People hunted large mammals for meat and hides, but environmental and
territorial constraints meant that only small numbers of a limited range of
species were available. Indeed, large mammals constitute a very small
proportion of the faunal remains found at archaeological sites, and only three
species are represented: the hartebeest, the dorcas gazelle, and a type of
wild cattle called the aurochs. Birds—particularly coots and migratory geese
and ducks—were caught regularly. Fish, however, were by far the most
important source of protein—primarily catfish. For carbohydrates, the Nile
Valley offered its inhabitants a considerable variety and seasonal abundance.
Twenty-five different seeds, fruits, and soft vegetable tissues have been
distinguished among archaeological remains.
8.According to paragraph 7, what did the remains found at archaeological sites
reveal about the food eaten by inhabitants of the Nile Valley?
A Small mammals were one of the most important food sources.
B Large mammals were not a major source of food.
C Birds were eaten more regularly than fish.
D Carbohydrates were eaten much less often than protein.
9.Look at the four squares that indicate where the following sentence could be added
to the passage
People moved away from the desert in various directions.
Where would the sentence best fit？Click on a square sentence to the passage.
10.Together the Nile River and Sahara desert helped shape the development of
agriculture and settled human society in Africa.
Select 3 answers
A The regular flooding of the Nile forced people into the deserts, where they survived by
hunting and gathering until they could return to their sedentary lifestyle in the Nile Valley.
B The Nile Valley could not support agriculture until the last glacial maximum, at which
time the slow, narrow Nile River became the wide, powerful river that we know today.
C Although the Nile Valley supported few large animals and space was limited, the
wildlife and seasonal foods available were sufficient to support populations established
along the Nile.
D Long before the founding of ancient Nile civilizations that depended on crops of
Southwest Asian origin, agriculture based on indigenous plants was practiced in the
Sahara.
E Increasing aridity drove people out of the Sahara, and the more crowded conditions
that this created in the Nile Valley forced people moving there to become sedentary.
F Recent archaeological evidence suggests that hunting and fishing played a very minor
role in the Nile Valley in comparison with food cultivation.

答案：1A 2D 3D 4D 5B 6C 7C 8B 9A 10CDE
 Chondrites 3.1
Meteorites are the keys to understanding how Earth and the solar system
formed because, although superficially many meteorites do not look
significantly different from most Earth rocks close study shows that they are
very different, With those differences holding clues to their distant origin. The
most common type of meteorite-known collectively as the"chondrites-contains
clues about the kinds of material that went into the construction of our planet.
1.Which of the sentences below best expresses the essential information in the
highlighted sentence in the passage? Incorrect choices change the meaning in
important ways or leave out essential information
A To understand how our solar system formed, it is important to determine the differences
between Earth rocks and meteorites
B Despite their similar outward appearance, meteorites and Earth rocks are really very
different, and the differences help explain how our solar system formed
C The superficial similarity of meteorites to Earth rocks provides clues about how our solar
system formed
D While meteorites had a distant origin, their presence on Earth is a key to understanding
how our solar system formed
The chondrites are just one of a variety of meteorite types, all ancient, but
each with a different history-and each containing clues about how Earth and
other planets formed and evolved. For example, the members of one group,
the iron meteorites, are made up of solid iron metal, alloyed (or mixed )with a
modest amount of nickel All the evidence indicates that these meteorites are
similar to the metallic cores that inhabit the interiors of planets.
2.According to the information in paragraph 2, which of the following is true about
iron meteorites?
A They are much more ancient than the chondrites
B They are less similar to planets’ metallic cores than chondrites
C They came to Earth from other planets
D They are solid metal objects
In contrast to the iron meteorites. the chondrites are made up of a jumble of
mineral grains, many of them familiar constituents of rocks on Earth, but also
including pure iron metal-which does not occur in rocks on Earth-and small
marble-like spherical objects called"chondrules"(it is from these that the
chondrites take their name). The chaotic texture of chondrites indicates that
they were formed in a process that randomly swept together their different
components and cemented them together. The texture is also an instant clue
to one of their most important characteristics: they have never been melted.
Furthermore, mineral grains in the chondrites have provided the oldest ages
ever measured by radiometric dating they date from the very earliest days of
the solar system. These two properties have led the geochemists who work
on these intriguing objects to conclude that chondrites bring us something we
cannot find on Earth or among other meteorite varieties: an unprocessed
sample of the original material from which Earth and our neighboring planets
were made. They appear to be unaltered samples of the solid matter that was
floating around in the solar system just as Earth was being born; there is
strong evidence that they come from small asteroids that never grew big
enough to heat up and melt, as larger objects did.
3.The word “chaotic” in the passage is closest in meaning to
A characteristic
B disorganized
C smooth
D unusual
4.According to paragraph 3, which of the following is indicated by the texture of
chondrites?
A They were formed by the same process as the rocks on Earth
B They are made of metals and minerals of different ages
C They have never been melted
D They are held together by a marble-like material
5.According to paragraph 3, which of the following can be inferred about the origin
of chondrites?
A They resulted from mixing and joining of many of the same materials that also formed
Earth and its nearby planets
B They were created when large asteroids broke apart as they neared early Earth
C They resulted from the repeated melting and hardening of other kinds of meteorites
during the long process of Earths formation
D They formed from the heating up of small asteroids as they entered early Earth's
atmosphere
The primitive nature of the chondrites has made them very important for
information about Earths overall chemical composition. You might wonder why
these rare rocks from space should play such a key role when the Whole
Earth Is right below our feet, ready for us to analyze. The answer, In brief, is
that if we want to understand how Earth got to its present state, we have to
know something about its initial, overall composition. But we only have access
to rocks from our planets thin outermost skin-which is very different from the
inaccessible interior. However, by using information from the chondrites as a
reference point, and integrating that data with direct measurements on
surface rocks and information about the interior obtained using remote
sensing methods, geochemists have been able to work out models for Earths
overall composition that satisfy already obtained independent evidence such
as the density of our planet.
6.In describing our planets interior as “inaccessible”, the author means that the
interior
A cannot be reached
B is very deep
C has a very high temperature
D formed a long time ago
7.According to paragraph 4, studying chondrites helps scientists learn about
which of the following?
A Earths overall density
B The chemical composition of Earths surface rocks
C Earth's original composition
D The age of Earth
An important concept in formulating these models is that the composition of
Earth and the other"terrestrial planets(the solar systems inner, rocky planets,
Mercury, Venus, and Mars)depends on the proportions of the main minerals
found in the chondrites that each planet incorporated, A good example is iron,
which is so abundant and so heavy that the well-known density variations
among the terrestrial planets can almost entirely be attributed to differences in
their iron contents. Grains of iron metal are abundant in the chondrites, but
different chondrites contain different amounts. The reason Earth is much
denser than Mars, according to the models, is that its chondrite-like building
blocks happened to contain more iron. Similarly, other differences among the
terrestrial planets can be understood in terms of different planets
incorporating different amounts of the various constituents of chondrites. This
is undoubtedly an overly simplistic description of what actually happened, but
that does not invalidate the chondrites as a good starting point for
understanding the composition of Earth and other planets.
8.In paragraph 5, why does the author mention that different chondrites contain
different amounts of iron?
A To suggest that some types of chondrites affected planets more than did others
B To help explain the differences in the densities of the terrestrial planets
C To indicate one Important reason why using chondrites as a model for understanding
the composition of Earth may be overly simplistic
D To emphasize the importance of iron in forming the terrestrial planets
9.Look at the four squares that indicate where the following sentence could be
added to the passage
What is more, geochemists have used these ancient rocks to explain the workings of
Earth’s crust, oceans, and other geological systems.
Where would the sentence best fit？Click on a square sentence to the passage.
10.Meteorites known as chondrites contain clues about the materials that went into
the construction of the terrestrial planets. Select 3 answers
A There are a number of different types of chondrites, which are distinguished by their
different histories and the amounts of solid iron and nickel metal alloyed in their metallic
cores
B The age of chondrites can be determined by radiometric dating of the small marble-like
spheres that, along With various mineral grains, were cemented together to make them
up
C Various minerals occur in different proportions in different chondrites suggesting that
many differences among planets stem from their having incorporated different amounts of
these minerals
D Chondrites are made up of ancient grains, including pure iron, that appear to be
unaltered samples of the solid material present in the solar system when Earth was
forming
EInformation from chondrites has enabled geochemists to develop models for Earth's
initial. overall chemical composition despite their lack of direct access to Earth's interior
FIron is by far the most abundant of the main minerals found in chondrites. and this fact
has been central to the formation of models of the composition of Earth and the other
terrestrial planets

答案：1B 2D 3B 4C 5A 6A 7C 8B 9A 10CDE
 Mars's Disappearing Atmosphere 3.1
For about the first billion years of its life, Mars was probably a watery planet.
There are signs of past water in surface features, such as dried riverbeds, and
in minerals that could only have formed in the presence of water. For there to
have been water, early Mars must have had a thick atmosphere secured by a
magnetic field. While Mars and Earth seem superficially similar, Earth has a
magnetic field that helps to protect and retain its atmosphere, whereas Mars
lost its magnetic field long ago, and its atmosphere is about 100 times thinner
than Earth's. Mars's atmosphere may have disappeared in two different ways:
up into space, and down into the ground (to become locked up within rocks
and soil.) Observations by the spacecraft MAVEN have suggested that an
"escape to space," in which the solar wind (electrically charged particles
streaming out from the Sun) strips away material from the upper parts of a
planetary atmosphere, is probably most to blame. This process is still taking
place today with what is left of the Martian atmosphere.
1.According to paragraph 1, all of the following were probably true of early Mars
EXCEPT:
A It had rivers flowing on its surface.
B It had minerals that were formed in the presence of water.
C It had a magnetic field.
D It had an atmosphere that was 100 times thinner than Earth's atmosphere today.
2.Which of the following best describes the relationship of paragraph 2 to
paragraph 1 with regard to the discussion of the loss of Mars's atmosphere?
A Paragraph 2 discusses an alternative to the explanation said to be the most likely one in
paragraph 1.
B Paragraph 2 explains why the theory discussed in paragraph 1 is now considered to be
correct.
C Paragraph 2 suggests that the process identified in paragraph 1 can account for only part of
what happened.
D Paragraph 2 provides the details of the process that is introduced as a likely explanation in
paragraph 1.
The solar wind streams into Mars's vicinity, interacts with its atmosphere, and
removes its uppermost ions (charged particles), dragging them out into space.
The early Sun was far more volatile and active than the later Sun, flinging out
bursts of radiation and producing solar storms far more frequently. This could
have made any atmospheric stripping up to 20 times more devastating.
Once Mars's magnetic field switched off, after half a billion years or so, the
planet's upper atmosphere would have been naked, lacking its former shield.
The solar wind could have streamed in and ionized molecules at a far higher
rate, stripping them away faster.
3.According to paragraph 2, which TWO of the following factors caused Mars to
lose its atmosphere at a fast rate? To receive credit, you must select TWO answer
choices. Select 2 answers
A The Sun was closer to Mars in its early days.
B The presence of ions out in space created bursts of radiation.
C The early Sun frequently produced solar storms.
D Mars lost its magnetic field, which had protected the atmosphere.
There is also the fact that Mars is smaller, is less heavy, and thus has lower
surface gravity than Earth. Accordingly, the planet simply struggles to keep
hold of as much atmospheric material as Earth can. Mars's atmosphere also
may have been blasted out into space by the disastrous collisions with large
objects we know to have taken place during its early history (which in turn
would have made subsequent impacts even more destructive due to the
thinner Martian atmosphere, continuing and worsening the cycle). In a less
exciting scenario, Mars's atmosphere might have just spun off into space of its
own accord-the molecules may have swirled around and around, colliding and
transferring energy between themselves, growing faster and faster until they
moved fast enough to escape.
4.The word“Accordingly”in the passage is closest in meaning to
A Most likely
B In addition
C In fact
D Therefore
5.Which of the sentences below best expresses the essential information in the
highlighted sentence in the passage? Incorrect choices change the meaning in
important ways or leave out essential information
A When the molecules in Mars's atmosphere began aswirl ing around, they produced enough
energy to cause them to collide and exchange some of that energy.
B If the collisions of molecules had failed to produce enough energy, Mars's atmosphere might
have escaped into space of its own accord.
C Mars might have lost its atmosphere because of its molecules colliding and gaining speed
until they moved so fast that they escaped into space.
D The collisions among the molecules in Mars's atmosphere might have caused them to swirl
around at a faster and faster rate.
6.Which of the following can be inferred from paragraph 4 about the theory that
Mars's atmosphere disappeared into the surface of the planet?
A It is not supported by the chemical analysis of Martian meteorites.
B It is supported by newer investigations of the carbonate content of Martian soils.
C It can explain only a small part of the loss of the planet's atmosphere.
D It is probably the best explanation for the loss of Mars's atmosphere.
At least some of Mars's atmosphere is thought to have headed down into the
planet's surface layer, interacting with the soil and combining with the
elements present there, a process known as sequestration. We see signs of
this process in the few Martian meteorites we have found here on Earth and in
the explorations of the United States space agency's Curiosity rover, which
saw further signs when it arrived on Mars and began to study the soil and
atmosphere in earnest. However, we have found that this is unlikely to have
been a dominant process; we would expect the heavier parts of Mars's
atmosphere to have disappeared if it were, as they would have sunk down
and been the ones to interact with the Martian surface. We see the opposite:
instead of an atmosphere filled with lighter forms of the constituent elements,
we see heavier ones. This suggests that Mars's atmosphere was stripped
from above and not below, thus removing more of the lighter elements and
leaving the heavier ones behind. We would also expect to find carbonates,
compounds that are a consequence of sequestration, in the Martian soil, but
despite our various searches these do not seem to be present in large
amounts.

We are still unsure of exactly what happened with Mars's atmosphere but are
fairly confident that the planet was once wrapped in a far thicker atmosphere
that allowed the planet to stay warm and pressurized enough to support
bodies of running and standing water. Mars's ancient atmosphere was likely
different in composition, with a far higher amount of oxygen, a necessary
component of water We know this because we have found minerals in old
Martian rock that need either an oxygen-rich environment or one with
microorganisms present in order to form, and we do not believe it to have
been the latter.
7.The word"fairly" in the passage is closest in meaning to
A reasonably
B absolutely
C cautiously
D increasingly
8.According to paragraph 5, which of the following evidence leads scientists to
believe that Mars's ancient atmosphere had much more oxygen than it has today?
A Rock that could only have formed in temperatures warmed by a thick atmosphere
B The presence of microorganisms in old Martian rock
C Certain minerals found in old Martian rock
D Rock that seems to have been shaped by running and standing water
9.Look at the four squares that indicate where the following sentence could be
added to the passage
But the lack of a magnetic field and the Sun's activity may not have been the only
contributors to the loss of atmosphere.
Where would the sentence best fit？Click on a square sentence to the passage.
10.Much research has been done on Mars's past atmosphere. Select 3 answers
A In order to have the pressure and temperature necessary to retain water, Mars's early
atmosphere must have been thicker than the planet's current atmosphere.
B Most of Mars's early atmosphere may have escaped into space as a result of the action of
the solar wind on the upper atmosphere.
C The surface gravity of Mars may have increased as a result of the heavier materials that sank
down into the surface of Mars.
D After the upper atmosphere was lost, large objects from space entered and destroyed the
remaining atmosphere at a far greater rate than earlier in the planet's history.
E Some of the material in Mars's early atmosphere could have entered the planet's surface
layer, where it interacted with the soil to form compounds that remained there.
F Martian rock samples recovered by recent space explorations suggest that Mars's
atmosphere today contains more oxygen than was previously thought to be present.

答案：1D 2D 3CD 4D 5C 6C 7A 8C 9C 10ABE

 Martian Volcanoes 3.15
Earth is not the only planet to have volcanoes; in fact Mars-though all of its
volcanoes have long been inactive-has the two largest ones in the solar
system: Olympus Mons and Alba Patera. Mars has spectacular lava fields,
large craters formed by a volcanic explosion, and shields (broad, low
volcanoes shaped like shallow domes).
1.The word "longevity" in the passage is closest in meaning to
A length of life
B level of activity
C composition
D distribution
The most striking characteristic of Martian volcanoes is in fact their great size
and longevity. The giant shields of Tharsis and to a lesser extent the
volcanoes of Elysium and Hellas pack in many times more lava than the
largest volcanoes on Earth, and yet Mars is a smaller planet. The reason lies
in the planets' internal makeup. Because it is larger and hotter, Earth has a
nearly molten (hot liquid) mantle that is overlain by a very thin rock crust-less
than 10 kilometers thick under the ocean basins. The hot mantle churns
over in great loops, and rips the overlying rigid crust into great slabs, called
tectonic plates, that shuffle around the globe. In those places where deep-
seated "hot spots" send plumes of molten material to the surface, the magma
(the trapped lava) starts piling up on the crust to build a volcano, but because
the crust is drifting, the volcano eventually breaks away from its source and
goes extinct. In its place, a new volcano starts to grow, so that a hot spot
under a mobile plate creates a string of medium-sized volcanoes rather than
one giant shield.
2.In paragraph 2, why does the author provide the information that Mars is smaller
than Earth?
A To clarify a common misconception about Mars
B To help explain the size of Earth's volcanoes
C To emphasize the surprising size of Martian volcanoes
D To indicate essential differences between the two planets
On the smaller, faster-cooling Mars, the crust has solidified and thickened to
the extent that it remains stationary with respect to the underlying hot spots.
When a plume of magma erupts at the surface, it will build a single volcano in
one place for as long as the supply lasts-typically hundreds of millions of
years. Not surprisingly, then, the volume of one Martian shield like Olympus
Mons or Alba Patera is comparable to that of an entire chain of volcanoes on
Earth, such as the Hawaiian Emperor chain that stretches across the Pacific
and spans nearly 100 million years of hot-spot activity.
3.Which of the sentences below best expresses the essential information in the
hiahliahted sentence in the passage? Incorrect choices change the meaning in
important ways or leave out essential information.
A A comparison of the Hawaiian Emperor chain. Olympus Mons.and Alba Patera shows they
are all about 100 million years old.
B The volume, then. of one Martian shield is comparable to the entire number of volcanoes on
Earth, spanning nearly100 million years
C Logically. then, the volume of a single Martian shield is about the same as a chain of
volcanoes on Earth.
D A chain of volcanoes like Earth's Hawaiian Emperor chain would take nearly 100 million
years to form on Mars.
4.According to paragraph 3, why do volcanoes grow larger on Mars than they do
on Earth?
A The underlying hot spots erupt from much greater depths on Mars than on Earth.
B The magma on Mars is not as thick as on Earth, allowing for faster expansion.
C The interior of Mars has a larger supply of magma than does the interior of Earth.
D The thicker crust on Mars allows volcanoes to grow in the same place for much longer
periods.
Another characteristic of Martian volcanoes is the large size of their craters
and the long run-out distances of their lava flows. This is principally due to the
lower gravity on Mars: 38 percent, or about one third, of Earth's gravity.
Gravity controls to some extent how solid rock behaves under stress. When
the crust stretches and breaks in a low gravity field, as it does on Mars, the
fissures that open up are wider than on Earth and can funnel larger amounts
of magma toward the surface.
5.According to paragraph 4, the low gravitational field of Mars causes
A fissures in the rocks to be quite large
B magma to flow more slowly to the surface
C the planet's crust to break more often
D magma chambers to last longer
Magma chambers grow correspondingly larger and when they empty out and
collapse, they yield larger craters. Eruption rates also tend to be higher on
Mars, since greater quantities of lava can flow out of the wider fissures. These
larger volumes guarantee a better retention of heat. Because it stays hot and
molten for a longer period of time, lava on Mars travels greater distances than
it does on Earth before cooling and slowing to a halt.
6.The word"retention" in the passage is closest in meaning to
A intensity
B dispersal
C production
D conservation
7.According to paragraph 5, why does molten lava stay hotter on Mars's surface
than on Earth's?
A It comes from hotter sources.
B It has been under the crust longer.
C It travels shorter distances.
D It flows in larger amounts
Explosive eruptions are also affected by the unique set of conditions that exist
on Mars. The atmospheric pressure is so low that any gas bubbles trapped in
the magma will undergo tremendous expansion upon reaching the surface. As
a result, it will take lesser amounts of dissolved gases in Martian (versus
terrestrial)magma for the mixture to foam and shoot out explosively from the
vent. On Earth, the confining pressure of the atmosphere requires that
magma contains close to 1 percent (by weight) of light gases for it to spray
upward as a lava fountain. About 3 to 4 percent is needed for the bubbles to
grow large enough to blow the magma to shreds and create an ash cloud. On
Mars, thresholds for such disruptive behavior are much lower: respectively
0.03 and 0.2 percent gases by weight. Twenty to thirty times less gas is
needed on Mars to achieve similar results.
8.Assuming that terrestrial and Martian magma have similar levels of gas. which of
the following can be inferred from paragraph 6 about Martian volcanic eruptions?
A They are less affected by atmospheric pressure levels than by other atmospheric
conditions.
B They produce ash clouds more frequently than terrestrial eruptions do.
C They include lava sprays 3 percent to 4 percent of the time
D They produce lava fountains less often than they produce ash clouds.
9.Look at the four squares that indicate where the following sentence could be
added to the passage
These series of volcanoes will continue to be created until the source of lava dries
up.
Where would the sentence best fit？Click on a square sentence to the passage.
10.The unique characteristics of Mars have created the largest volcanoes in the
solar system. Select 3 answers
A Although it is smaller than Earth, Mars is hotter, and its mantle, the layer of molten rock
beneath the crust, is larger.
B Volcanoes on Earth are much smaller than those on Mars because Earth's moving crust
causes the volcanoes to go extinct quickly.
C Mars's solid crust and low gravity and atmospheric pressure create large volcanoes that
release large amounts of lava for a long time.
D Mars's volcanoes, like those on Earth, begin when hot spots deep in the molten mantle
release streams of magma up through the surface crust
E The many extremely large volcanoes on Mars have caused the planet's crust to thicken and
remain stationary.
F The release of gases from magma on Mars causes the magma to cool down much more
quickly than it does on Earth.

答案：1A 2C 3C 4 5A 6D 7D 8B 9D 10BCD
 Chinampas 3.15
In the fifteenth and sixteenth centuries, the Aztec empire stretched across
what is now central and southern Mexico and included both highlands and
lowlands. On relatively flat lowlands and in some shallow lake beds,
irrigation agriculture was the rule. In these areas, floodwater irrigation
systems were constructed over large areas. The soils were fortified and
replenished by nutrients and soil particles carried in the water; thus, the need
for fallowing (leaving land uncultivated for a time) was eliminated. Irrigation
was far more intensive than the fallowing technique, providing greater
surpluses and supporting larger populations. Crop rotation and fertilizers may
have been used to further increase yields. Lands with easy access to natural
springs could be irrigated permanently with spring water. Springs were
numerous in the southern part of the Basin of Mexico, and vast systems of
irrigation agriculture were concentrated there. These permanent systems,
along with floodwater networks favorably situated near springs, could draw on
water supplies prior to the onset of the rainy season. Crops could be planted
early and mature with certainty before the frost season began. Reliability of
production, therefore, was relatively high.
1.The word "concentrated" in the passage is closest in meaning to
A maintained
B in continuous operation
C present together in large numbers
D constructed
2.According to paragraph 1, the use of irrigation agriculture allowed the Aztecs to
have greater control over
A how much their crops benefited from the rainy season
B when their crops reached maturity
C how often their crops had to be rotated
D how much water was present in natural springs
The most intensive form of irrigation agriculture was the chinampas.
Chinampas were highly productive plots of land claimed from the shallow
beds of freshwater lakes. These long, rectangular fields ranged in size from
two to four meters wide and twenty to forty meters long and rose about one
meter above water level. Misnamed "floating gardens," chinampas are still
cultivated in and around Xochimilco and neighboring cities and are a popular
tourist attraction. A chinampa was constructed by piling alternating layers of
vegetation and mud in shallow areas of lakes. The parcel was held secure at
first by posts, and later, when the plot was established, by the roots of willow
trees planted at the corners and along the sides. The entire plot thus served
as a deep, humus-filled foundation for continuous cultivation. It was bordered
by canals and walkways, and dipping into an adjacent canal provided
irrigation. Although nutrients constantly replenished the soil in this manner,
other fertilizers, crop rotation, and multiple cropping were probably used to
increase production.
3.According to paragraph 2, all of the following were characteristics of he Aztecs'
chinampas EXCEPT
A They were long and narrow
B Their soil was held in place in part by tree roots.
C Their layers of vegetation and mud had to be replaced every year.
D They were irrigated with water from canals that ran along their sides.
4.Paragraph 2 suggests which of the following about the construction of
chinampas?
A They were only built in and around urban areas
B They were produced when shallow lakes were drained.
C They were attached to the lake bed and did not actually float in the water.
D They had canals running through them
A variety of crops were grown on chinampas, including maize, beans, chiles,
amaranth, tomatoes, and flowers. There are good indications that, like today,
the chinampa farmers planted their seeds in small seedbeds, allowed them to
germinate there, and then transplanted them throughout the chinampa. Maize,
apparently, was the only crop that could bypass this stage. The seedbed
technique assured greater returns, since only germinated plants were
transplanted. Furthermore, it allowed the cultivator some overlap in cropping:
while one crop was about to be harvested, another could be germinating in
the seedbeds. This would have reduced the intervals between croppings.
Today, and probably in the sixteenth century, seven different crops are
possible on any chinampa annually.
5.Why does the author provide the information that “while one crop was about to
be harvested, another could be germinating in the seedbeds?”
A To present a method that was used as an alternative to the seedbed technique
B To support the claim that only germinated plants were transplanted to seedbeds
C To suggest a reason why the chinampas of today may be as productive as those in the
sixteenth century
D To illustrate an advantage of the seedbed technique
6.According to paragraph 3. which of the following is true of how crops were
grown on the chinampas?
A Regions that focused on maize generally did not grow other crops on their chinampas.
B The techniques used in the sixteenth century were likely very different from those used on
the chinampas today.
C At least seven different crops were planted at the same time because some crops did not
germinate on the chinampas.
D Probably every crop except maize was started in a seedbed and then transferred to the
chinampas after germination.

While the intensiveness, reliability, and versatility of this system cannot be

overemphasized, it must be placed in the context of the population it
supported. After extensive investigations of sixteenth-century documents,
Edward Calnek has concluded that: "The larger chinampa holdings would
normally have provided no more than 15 percent of family subsistence
income; in a large number of cases, the actual contribution must be estimated
at a fraction of 1 percent of family needs. With respect to the smaller sites, it is
difficult to imagine why chinampas were maintained at all." Calnek provides
an answer by suggesting that the value of the plots lay less in their overall
productive yields than in their specialization in the production of fresh
vegetables. Flowers also were an important perishable that could be
produced on the urban chinampas; hardly a religious festival or political feast
took place without an abundance of aromatic flowers. In these areas, a family
may have met subsistence needs through advantageous marketplace
exchanges of their specialized products or through allocations from the state.
Outside the densely populated urban areas, chinampas plots were generally
larger and resident families smaller. Such a family could probably not only
fully support itself from its own chinampas production but also produce
sizeable surpluses. This applied particularly to the southern lakeshores of the
Basin of Mexico, around Xochimilco and Chalco, which had the greatest
number of chinampas.
7.According to paragraph 4. families in urban areas may have met their
subsistence needs in which of the following ways?
A By living mostly off the crops from their own chinampas
B By growing and trading specialized products
C By relying on the proceeds they received from selling their surpluses to people from rural
areas
D By supplying fresh vegetables for religious and political events
8.According to paragraph 4. which of the following is true of the chinampas around
Xochimilco and Chalco?
A They produced enough to fully support their resident families with some left over.
B They were located near urban areas that had large marketplaces.
C They were worked by large resident families who each owned a small portion of their plots.
D They were more productive than the chinampas near the southern lakeshores of the Basin
of Mexico.
9.Look at the four squares that indicate where the following sentence could be
added to the passage
Different parts of the empire required different agricultural techniques
Where would the sentence best fit？Click on a square sentence to the passage.
10.In the fifteenth and sixteenth centuries, the Aztecs grew crops using
chinampas, a unique form of irrigation agriculture. Select 3 answers
A Chinampas were preferable to other types of irrigation agriculture that used natural springs
because springs went dry for part of the year
B Most of the various crops grown on chinampas started out as seedlings in seedbeds and
were transplanted later, increasing output and allowing for overlap between crops
C Unlike the original chinampas, today's floating gardens in Xochimilco and neighboring cities
produce multiple croppings without the need for seedbeds.
D Common in the southern part of the Basin of Mexico, chinampas were rectangular fields
constructed in shallow lake beds out of alternating layers of vegetation and mud.
E In some rural areas chinampas could support the families who worked them, but in urban
areas chinampas probably provided only specialized products such as vegetables and
flowers.
F Chinampas were significant for the large quantities of a wide variety of crops they produced,
allowing farmers to cultivate specialized crops on non-irrigated fields

答案：1C 2B 3C 4C 5D 6D 7B 8A 9A 10BDE
 Economic Reasoning 3.15
Economics begins with the assumption that human actions are rational-
intended for maximum self-benefit. For example, people pay more for a larger
box of the same cereal than for a smaller one. Yet people sometimes seem to
act irrationally. When a celebrity endorses a product, sales increase although
the endorsement appears to convey no information about product quality.
Nonetheless, economists stubbornly insist on finding rational explanations for
all behavior. Why? Imagine a physicist who encounters his first helium-filled
balloon. which flies up rather that down when released near the ground, a
blatant challenge to the laws of gravity. Two courses are open to him. He can
say. "Well. the laws of gravity have exceptions." Or he can say, "Let me see if
there is any way to explain this strange phenomenon without abandoning
basic principles of physics." If he takes the latter course, and if he is
sufficiently clever. he will eventually discover the properties of objects that are
lighter than air and recognize that their behavior is in perfect harmony with
existing theories of gravity. In the process he will not only learn about helium-
filled balloons; he will also come to a deeper understanding of how gravity
works.

1.The word "blatant" in the passage is closest in meaning to

A seeming
B confusing
C obvious
D practical
2.In paragraph 1, why does the author discuss celebrity endorsements?
A To argue that product size can be more important for sales than quality
B To show that celebrities act for their own self-benefit
C To warn against buying products without information about their quality
D To provide an example that challenges a basic assumption of economics
3.In paragraph 1, why does the author discuss an imaginary first encounter of a
physicist with a helium-filled balloon?
A To demonstrate that even the laws of gravity are not fully understood
B To identify the properties of objects that are lighter than air
C To suggest that assumptions in economics are more likely to have exceptions than are the
laws of physics
D To demonstrate that economists are right in looking for rational explanations for all human
actions

Now it might very well be that there are real exceptions to the laws of gravity,
and that our physicist will one day encounter one. If he insists on looking for a
good explanation without abandoning his theories, he will fail. If there are
enough such failures, new theories will eventually arise to supplant the
existing ones. Nevertheless the wise course of action, at least initially, is to
see whether surprising facts can be reconciled with existing theories. The
attempt itself is a good mental exercise for the scientist, and there are
sometimes surprising successes. Moreover, if we are too quick to abandon
our most successful theories, we will soon be left with nothing at all.

4.Paragraph 2 mentions which TWO of the following benefits of trying to reconcile

exceptions with existing theories? To receive credit, you must select TWO
answers. Select 2 answers
A Reduced risk of failure
B Exercise of the mind
C The possibility of an unexpected success
D The possibility that new theories will arise quickly

Much primitive agriculture shares a strange common feature. There are very
few large plots of land: instead each farmer owns several small plots
scattered around the village. (This pattern was endemic in medieval England
and exists today in less developed parts of the world.) Historians have long
debated the reasons for this scattering, which is believed to be the source of
much inefficiency. Perhaps it arises from inheritance and marriage: At each
generation, the family plot is subdivided among the heirs, so that plots
become tiny; marriages then bring widely scattered plots into the same family.
This explanation suffers because it seems to assume a form of irrationality:
Why don't the villagers periodically exchange plots among themselves to
consolidate their holdings?

5.Paragraph 3 suggests that historians have offered which of the following

explanations for the kind of land plots that medieval farmers owned in England?
A Agriculture was too primitive for farmers to work large plots of land efficiently
B Families subdivided their land when a family member became married
C Land could be divided among several people when it was passed on to the next generation.
D Villagers often exchanged small plots of land among themselves.

Inevitably. this problem attracted the attention of the economist and historian
Deirdre McCloskey. whose instinct for constructing ingenious economic
explanations is unsurpassed. Instead of asking "What social institutions led to
such irrational behavior?" McCloskey asked, "Why is this behavior rational?"
Careful study led her to conclude that it is rational because it is a form of
insurance. A farmer with one large plot is liable to be completely ruined in the
event of a localized flood. By scattering his holdings, the farmer gives up
some potential income in exchange for a guarantee that he will not be wiped
out by a local disaster. This behavior is not even exotic. Every modern insured
homeowner does the same thing. One way to test McCloskey's theory is to
ask whether the insurance "premiums" (that is, the amount of production that
is sacrificed by scattering) are commensurate with the amount of protection
being "purchased." using as a standard the premiums that people are willing
to pay in more conventional insurance markets, and by this measure it holds
up well. A serious criticism is this: If medieval peasants wanted insurance,
why didn't they buy and sell insurance policies, as we do today? A simple
answer is that nobody had yet figured out how to do it. But some economists
demand more exact answers to this objection, and they are right. Theories
should be tested to their limits.

6.The phrase "this problem" in the passage refers to

A the continued inefficiency of agriculture in some parts of the world
B the need for villagers to consolidate their holdings
C the lack of a rational explanation for plot scattering
D the role of inheritance and marriage in the size of plots
7.Which of the sentences below best expresses the essential information in the
highlighted sentence in the passage? Incorrect choices change the meaning in
important ways or leave out essential information.
A The amount of production sacrificed by scattering is commensurate with what people are
willing to pay for protection in more conventional insurance markets. which supports
McCloskey's theory
B The amount of protection people have been purchasing by buying insurance has been
commensurate with the insurance premiums, and the standard used for measuring them has
held up well over time
C One way to test McCloskey's theory is to measure the amount of production that is
sacrificed by scattering and the "premiums" that people are willing to pay for that production
on the market.
D One way to test McCloskey's theory is to ask people whether the "premiums" they are
willing to pay in more conventional insurance markets are commensurate with the protection
being "purchased
8.According to paragraph 4, which of the following explanations has McCloskey
provided for the practice of farmland scattering?
A Other available forms of insurance would be too expensive for the farmers
B The practice makes certain that farmers will not lose all their crops if a local flood occurs.
C The presence of social institutions can sometimes lead to irrational behavior.
D Farming several small pieces of land can be easier than farming a single large piece of land
9.Look at the four squares that indicate where the following sentence could be
added to the passage
This is because designing an insurance policy requires an act of genius.
Where would the sentence best fit？Click on a square sentence to the passage.
10.Economists try to explain certain decisions that humans make. Select 3 answers
A Economists have been able to explain why people pay different prices for products based
on their quantity but not why they do so when they have no information about product quality
B Economists believe that humans act in ways that are most beneficial or themselves,
although this belief may seem to be challenged by behavior like land scattering
C Land scattering during medieval times more likely resulted from an effort to reduce losses
at times of disaster than from the inheritance and marriage practices that were current then
D Economists are similar to physicists in that they usually explain surprising observations by
creating new theories instead of adding exceptions to existing ones.
E Economists and historians studying primitive agriculture could not agree on whether a
number of its practices are due to the traditions of inheritance and marriage or other social
institutions
F It is important to test theories to the greatest extent possible, but they should be abandoned
only when there are enough facts that cannot be brought into agreement with them.

答案：1C 2D 3D 4BC 5C 6C 7A 8B 9B 10BCF

 The First Eyes 3.15
Putting a date on the first appearance of eyes depends on what one means
by eye. If the term refers to a multicellular organ, even if it has just a few cells,
then by definition, eyes could not form before there were multicellular animals.
But many protists (animal-like, plantlike, or fungus-like unicellular organisms
that require a water-based environment) can detect light by using
aggregations of pigment molecules, and they use this information to modify
their metabolic activity or motility (the ability to move spontaneously and
independently). One of the familiar living examples, probably known to
anyone who has taken a biology class, is the aquatic protozoan Euglena,
which has an eyespot near its motile flagellum (hairlike structure). Some living
protists are very like their ancestral forms embedded in ancient sedimentary
rocks, and this similarity suggests that the ability to detect light and modify
behavior in response to light has been around for a very long time. Animals
arose from one of such unicellular creatures, perhaps from one already
specialized for a primitive kind of vision.
1.The word "aggregations" in the passage is closest in meaning to
A parts
B reactions
C groups
D types
2.Paragraph 1 supports all of the following statements about protists EXCEPT:
A Some are multicellular.
B Some are able to move.
C Some have pigment molecules.
D They live in environments that contain moisture.
3.According to paragraph 1, what have scientists concluded from the fact that
some living protists are very like their ancestral forms
A The eye did not evolve until multicellular organisms arose.
B The ability to detect light and change behavior in response to light has existed for a
long time.
C The ancestral forms of these living protists likely had an eyespot near the motile
flagellum.
D The ancestral forms of these living protists depended primarily on light as the
mechanism for modifying their metabolic activity or motility.

An eye is a collection of cells that are specialized for light detection through
the presence of photosensitive pigment as well as a means of restricting the
direction of incoming light that will strike the photosensitive cells. This
definition says nothing about image formation, lenses, eye movements, or any
of the other features we associate with our own eyes, but it does recognize
the simplest form of functional and anatomical specialisation namely,
detection of light. Everything else can be built up from this simple beginning,
and some animals appear to have had eyes almost from the beginning of the
animal kingdom.
4.Paragraph 2 implies which of the following about the early eyes
A They were able to detect simple movements almost from the beginning of their
evolution.
B They were not as sensitive to light as once thought.
C They could not form images.
D Their cells had more photosensitive pigment than do human eyes.

Animals were scarce 600 million years ago in the geological era called the
Precambrian. There are very few fossil remains from that time (though more
keep turning up), and most evidence of the presence of animals is indirect,
such as small tunnels in rock that could be ancient worm burrowings. But just
50 million years or so later, fossilized bits and pieces of animals abound,
suggesting that a great burst of evolutionary creativity occurred in the 50-
million-year interval. This surge of new life, marked by an abundance of
animals, is called the Cambrian explosion.
5.Which of the sentences below best expresses the essential information in the
highlighted sentence in the passage Incorrect choices change the meaning in
important ways or leave out essential information.
A There are few fossils from the Precambrian, though more keep turning up.
B Most evidence of animals in the fossil record is indirect and little of it is from the
Precambrian.
C Tunnels in Precambrian rocks that may have been made by worms provide indirect
evidence of these animals existing at that time.
D There are very few fossils of animals from the Precambrian and most evidence of
animal life from that period is indirect.
6.According to paragraph 3, the Cambrian period was characterized by
A a great abundance of animals
B a slow rate of animal extinction
C the rapid fossilization of animals
D an increase in the life span of some animals
The first direct evidence for the early origin of eyes comes from fossils that
are about 530 million years old, a time shortly after the Cambrian explosion;
they were found on a mountainside in British Columbia in a deposit known as
the Burgess Shale. The Burgess Shale fossils are extraordinarily important
because among them are remains of soft-bodied creatures, many of them
lacking shells and other hard parts that fossilize easily. Consequently, their
preservation is little short of miraculous (as are the delicate methods used to
reconstruct three-dimensional structure from these flattened fossils), and they
are one of the few known repositories of early soft-bodied animals.
7.The phrase "little short of miraculous" is closest in meaning to
A very highly valued
B amazing because almost impossible
C causing controversy
D almost but not quite complete
8.According to paragraph 4, all of the following are true of the Burgess Shale
EXCEPT:
A Its fossils were in a flattened condition when discovered.
B Its fossils provide direct evidence about the origin of eyes.
C It contains fossils of both Precambrian and Cambrian animals.
D It contains fossilized remains of soft-bodied organisms.

Not all of the Burgess animals had eyes. However, some did. (Gross
features location, size, and hemispheric shape are responsible for the
designation of some structures as eyes). The reconstructed eyes of these
Burgess animals look superficially like eyes of some living crustaceans,
particularly those of shrimp and crabs whose eyes are mounted on stalks that
improve the range of vision by raising the eyes above the surface of the head.
The eyes of some Burgess organisms sat on stalks; those of others were on
or a part of the body surface. One animal, Opabinia, had five eyes: two
lateral pairs and a single medial eye; at least one of the lateral pairs had
stalks that could have been movable. And some trilobite-like animals in the
Burgess Shale had faceted eyes much like those of later fossil trilobites.
9.The word "designation" in the passage is closest in meaning to
A evolution
B identification
C reconstruction
D confusion
10.The word "lateral" in the passage indicates a location at the
A front
B back
C top
D side
11.Why does the author point out that "The eyes of some Burgess organisms sat
on stalks"?
A To suggest that some Burgess organisms had a greater range of vision than do living
shrimp and crabs.
B To explain why it is thought that one of the lateral pairs of eyes in Opabinia may have
been movable.
C To explain why the eyes of some Burgess animals were not recognizable as such
before they were reconstructed.
D To support the statement that the reconstructed eyes of Burgess animals look
superficially like the eyes of some living crustaceans.

Although the presence of eyes on some of the Burgess animals indicates that
eyes have been around for a very long time, it is unlikely that these were the
first eyes; they seem much too large and (potentially) well developed to be
brand new inventions. The best we can do is put the origin of eyes
somewhere between the beginning of the Cambrian explosion, about 600
million years ago, and the death of the Burgess animals, some 530 million
years ago.
12.Paragraph 6 suggests that the first eyes probably
A came into existence long before 600 million years ago
B came into existence at a late point in the Cambrian period
C existed before the animals of the Burgess Shale existed
D were larger than those of animals found in the Burgess Shale
13.Look at the four squares that indicate where the following sentence could be
added to the passage
Molaria spinifera and H. optata, both of which lived in water levels beyond the
reach of light, fit into this category.
Where would the sentence best fit？Click on a square sentence to the passage.
14.It is difficult to determine the exact origins of the eye. Select 3 answers
A The ability of some unicellular organisms to detect light and change their behavior
accordingly suggests that eyes did not originate with multicellular animals.
B The earliest eyes apparently contained molecules that were capable of forming and
focusing images.
C Too few fossils from the Precambrian have been found to determine which if any
Precambrian organisms had eyes.
D Evidence from the Burgess Shale suggests that eyes of some early animals were
similar to the eyes of living crustaceans.
E Fossil evidence suggests that organisms in the Burgess Shale with faceted eyes
developed later than organisms in the Burgess Shale with nonfaceted eyes.
F The large size and possible complexity of the eyes of some organisms in the Burgess
Shale suggest that their eyes were not the first eyes.

答案：1C 2A 3B 4C 5D 6A 7B 8C 9B 10D 11D 12C 13A 14ADF

 Origin of the Solar System 3.22
The orderly nature of our solar system leads most astronomers to conclude
that the planets formed at essentially the same time and from the same
primordial (original) material as the Sun. This material formed a vast cloud of
dust and gases called a nebula. The nebular hypothesis suggests that all
bodes of the solar system formed from an enormous nebular cloud consisting
mostly of hydrogen and helium as well as a small percent of all the other
heavier elements known to exist. The heavier substances in this frigid cloud of
dust and gases consisted mostly of such elements as silicon, aluminum, iron,
and calcium—the substances of today’s common rocky materials. Also
prevalent were other familiar elements, including oxygen, carbon, and
nitrogen.
1.According to paragraph 1, which of the following best describes the “nebular
hypothesis”?
A Our solar system formed from a large cloud consisting mostly of hydrogen and helium
and of small amounts of other elements.
B Our solar system formed from gases and heavier elements thrown off by the Sun as it
rotated in the center of the nebular cloud.
C The primordial matter that evolved into our solar system consisted mostly of familiar
elements such as oxygen, carbon, and nitrogen.
D A cloud of dust and gases gathered into a rotating nebula composed mostly of the
rocky materials seen on Earth today.
2.The word “frigid” in the passage is closet in meaning to
A moving
B giant
C original
D cold
Nearly five billion years ago, some external influence, such as a shock wave
traveling from a catastrophic explosion (supernova), may have triggered the
collapse of this huge cloud of gases and minute grains of heavier elements,
causing the cloud to begin to slowly contract due to the gravitational
interactions among its particles As this slowly spiraling nebula contracted, it
rotated faster and faster for the same reason ice-skaters do when they draw
their arms toward their bodies. Eventually, the inward pull of gravity came
into balance with the outward force caused by the rotational motion of the
nebula. By this time the once vast cloud had assumed a flat disk shape with
a large concentration of material at its center, called the protosun (pre-Sun).
Astronomers are fairly confident that the nebular cloud formed a disk because
similar structures have been detected around other stars.

3.Which of the sentences below best expresses the essential information in the
highlighted sentence in the passage? Incorrect choices change the meaning in
important ways or leave out essential information.
A Possibly due to some explosion about five billion years ago, this nebular cloud began
to collapse, causing gravitational contractions as its particles interacted.
B About five billion years ago, a supernova may have exploded, causing a huge cloud of
gases and heavier elements to form
C Gravitational attraction among particles of gases and heavier elements caused some
explosive event nearly five billion years ago.
D About five billion years ago, a shock wave from an external event caused this huge
cloud of gases to collapse into small grains of heavier elements.
4.In paragraph 2, why does the author describe how ice-skaters use their arms to
increase their speed of rotation?
A To help describe the armlike structures on a spiraling nebula
B To help explain why a nebula rotates faster when it contracts
C To show why spinning ice-skaters are not pulled down by gravity
D To show how the motion of a nebula differs from that of an ice-skater
5.The word “detected” in the passage is closet in meaning to
A formed
B predicted
C discovered
D recorded
6.According to paragraph 2, why do astronomers believe that the nebular cloud
formed a disk around the protosun?
A They can still see some debris from the disk.
B They have observed that disks have formed around other stars.
C They know that any rotating cloud of gas tends to contract into a disk shape.
D They have conducted experiments with gravity that have confirmed their belief.

During the collapse, gravitational energy was converted to thermal energy

(heat), causing the temperature of the inner portion of the nebula to
dramatically rise. At such high temperatures, the dust grains broke up into
molecules and energized atomic particles. However, at distances beyond the
orbit of Mars, the temperatures probably remained quite low. At -200℃, the
tiny particles in the outer portion of the nebula were likely covered with a thick
layer of ices made of frozen water, carbon dioxide, ammonia, and methane.
Some of this material still resides in the outermost reaches of the solar system
in a region called the Oort cloud.

7.According to paragraph 3, which of the following best explains why the inner
part of the nebula became hotter as the nebula contracted?
A The nebula rose in temperature as its speed of rotation increased.
B Atomic particles in the nebula gave off more heat when they became energized.
C The dust grains broke up into smaller parts, allowing more light from the Sun to reach
the inner portion of the nebula.
D As the nebula collapsed, its gravitational energy was changed into heat energy
The formation of the Sun marked the end of the period of contraction and thus
the end of gravitational heating. Temperatures in the region where the inner
planets now reside began to decline. The decrease in temperature caused
those substances with high melting points to condense into tiny particles that
began to coalesce (join together). Such materials as iron and nickel and the
elements of which the rock-forming minerals are composed—silicon, calcium,
sodium, and so forth—formed metallic and rocky clumps that orbited the Sun.
Repeated collisions caused these masses to coalesce into larger asteroid-
size bodies, called protoplanets, which in a few tens of millions of years
accumulated into the four inner planets we call Mercury, Venus, Earth, and
Mars. Not all of these clumps of matter were incorporated into the
protoplanets. Rocky and metallic pieces that still remain in orbit are called
meteoroids.
8.Accordingto paragraph 4, the protoplanets formed by
A gravitational interactions among meteoroids
B increases in the gravitational pull of the Sun
C the warming of the nebular cloud
D collisions between materials orbiting the Sun
9.According to paragraph 4, all of the following occurred when the nebula stopped
contracting EXCEPT:
A Gravitational interactions between heavier elements decreased.
B Temperatures declined in the area of the inner planets.
C Some elements formed rocky masses that orbited the Sun.
D Protoplanets were formed.

As more and more material was swept up by the inner planets, the high-
velocity impact of nebular debris caused the temperatures of these bodies to
rise. Because of their relatively high temperatures and weak gravitational
fields, the inner planets were unable to accumulate much of the lighter
components of the nebular cloud. The lightest of these, hydrogen and helium,
were eventually whisked from the inner solar system by the solar winds.

At the same time that the inner planets were forming, the larger, outer planets
(Jupiter, Saturn, Uranus, and Neptune), along with their extensive satellite
systems, were also developing. Because of low temperatures far from the
Sun, the material from which these planets formed contained a high
percentage of ices—water, carbon dioxide, ammonia, and methane—as well
as rocky and metallic debris. The accumulation of ices partly accounts for the
large sizes and low densities of the outer planets. The two most massive
planets, Jupiter and Saturn, had surface gravities sufficient to attract and hold
large quantities of even the lightest elements—hydrogen and helium.

10.What can be inferred from paragraph 6 about the role that gravity on the outer
planets plays in their having low densities?
A The forces of gravity from the outer planets increase the speed of the solar winds,
causing the winds to carry away the heavier, denser elements.
B The outer planets’ strong gravities capture low-density ices from the outer reaches of
the solar system.
C Gravity on the outer planets is strong enough to prevent lighter elements from
escaping.
D The strong gravity on the outer planets results in high-velocity impacts with nebular
debris,causing their denser elements to be carried away into space.
11.The word “extensive” in the passage is closet in meaning to
A developing
B large
C complex
D centralized
12.The phrase “accounts for” in the passage is closet in meaning to
A explains
B creates
C encourages
D illustrates
13.Look at the four squares that indicate where the following sentence could be
added to the passage
In other words, as the outer parts of a rotating mass are pulled inward, the speed
of rotation increases.
Where would the sentence best fit？Click on a square sentence to the passage.
14.Our Sun and planets formed at about the same time from a collection of dust
and gases called a nebular cloud. Select 3 answers
A The early solar system was made mostly of heavier materials, such as rock-forming
minerals, with a small percentage of light elements such as hydrogen, helium,
oxygen,carbon, and nitrogen.
B As the outer parts of the nebular cloud cooled, they became home to a region of rocky
and metallic debris known as meteoroids.
C The inner planets formed when certain minerals collided and coalesced into larger
bodies with high temperatures and weak gravitational fields that were not able to retain
the lightest elements.
D Perhaps as the result of an explosive event, the nebular cloud collapsed and began
contracting as gravity caused to particles to interact.
E A supernova sent a shock wave through the nebular cloud, causing it to expand until its
heavier elements were forced to the outer solar system.
F Being farther from the Sun, the outer planets were cooler than the inner plants, giving
them a higher percentage of elements in the form of ice and a large quantity of the
lightest gases: hydrogen and helium.

答案：1A 2D 3A 4B 5C 6B 7D 8D 9A 10C 11B 12A 13B 14CDF

 Moonquake 3.22
Until 1969,scientists wondered if quakes happen on the Moon, and if so, if
they resemble quakes on Earth. Answers were provided by the lunar space
program of the United States. Beginning in November 1969， seismographic
stations were set up on the Moon during the landings of Apollo spacecraft
12,14,15,16,and 17. Special seismographs placed at the five landing sites
were operated continuously, sending back a steady stream of geophysical
data on the Moon's interior. Study of the location and mechanisms of
earthquakes has revealed a great deal about the way Earth is deforming; it
was expected that seismographs on the Moon would provide similar
information about its interior and deformation.
1.According to paragraph 1, which of the following was brought about by the
Apollo landings?
A Scientists began to use information about how the Moon is deforming to understand
how Earth is deforming.
B New, more sensitive seismographs were developed
C Scientists received important geophysical data related to the Moon's interior
D Unexpected discoveries were made about the location and mechanisms of quakes on
Earth.

But quakes on Earth are a consequence of the planet's massive dynamic

processes. In stark contrast to Earth, the Moon has, for millions of years,
been an unchanging planetary body with no visible active volcanoes and no
regions where the crust has split apart. It was therefore somewhat startling
that each of the lunar seismographic stations detected between 600 and
3,000 moonquakes every year, on the average. Most of the moonquakes
were tiny, with magnitudes of less than about 2 on the Richter scale. The fact
that the Moon has no atmosphere or oceans means that it has an extremely
quiet background, so that the seismographs can be operated with very high
magnifications, at least 100 to 1,000 times those that are normally possible on
Earth.
2.According to paragraph 2, why were scientists surprised by the information
acquired by the lunar seismographic stations?
A Most of the moonquakes were much smaller than the scientists had expected.
B They did not expect to find so many quakes, since they had no previous evidence of
volcanic activity or disruptions in the Moon's crust.
C They did not expect the average number of quakes to vary so much from year to year.
D They expected more background interference and were not sure the seismographs
could be operated at such high magnification.

Three different kinds of quake events are indicated. First are the deep
moonquakes, which have their centers at depths of 600 to 900 kilometers in
the Moon. These deep events are surprising. They seem localized at a
specific number of places in the Moon's interior, of which more than 40 have
been identified. At these active deep centers, moonquakes commonly occur
within an interval of a few days during perigee, the point at which the Moon's
orbit is closest to Earth. About equal numbers of deep moonquakes occur at
these centers at opposite phases of this tidal pull, so that the most active
periods are fourteen days apart. These periodic properties at least suggest
that Earth's tidal pull on the Moon triggers the occurrence of the deep seismic
energy releases. On Earth, similar conditions of the occurrence of
earthquakes with perigee have been sought for many years, but generally
without success.

3.Paragraph 3 indicates that scientists have tried for many years but have not
generally succeeded in finding which of the following?
A The effect of moonquakes on tidal pulls
B A link between perigee and earthquakes
C When deep seismic energy releases tend to occur in the Moon
D How the occurrence of earthquakes and moonquakes have changed over time
4.Which of the following can be inferred from paragraph 4 about surface
moonquakes?
A The Moon's surface experiences temperature changes that may create the tectonic
forces possibly responsible for the surface moonquakes
B Because surface thermal conditions on Earth vary so much from those on the Moon,
moonquakes occur more frequently than earthquakes.
C Scientists can predict the location of a surface moonquake with more accuracy than
that of a deep seismic event.
D Although they are very different in nature, surface moonquakes can be as powerful as
deep moonquakes.

The second type of moonquake occurs nearer the surface. These

moonquakes are not as common as the deeper events, and their locations do
not exhibit any particularly regular pattern over the surface of the Moon. It is
thought that, like most earthquakes, moonquakes are caused by the release
of tectonic strain in the rocks of the Moon's crust. If so, then either
groundwater is present in the Moon or some dry fracturing is occurring in the
unusual thermal conditions of the lunar surface, with its extreme range of cold
and heat.

The third type of seismic event results from the impact of objects, both natural
and artificial. The lunar seismographic stations were efficient detectors of
meteorites hitting the surface, even at a range of 1,000 kilometers. In order to
help with the determination of seismic-wave velocities of lunar rocks, parts of
the lunar spacecraft were programmed to crash back on the lunar surface.
These high- speed impacts generated seismic waves strong enough to
produce clear recordings at lunar seismographic stations, and because the
time and position of impact were known precisely, the travel times of the
seismic waves could be calculated easily. This calculation was the first step in
discovering the general architecture and properties of the Moon's interior.
5.According to paragraph 5, how were parts of the lunar spacecraft used to help
discover information about the Moon?
A They were sent deep under the Moon's surface to try to obtain information about deep
moonquakes.
B They were programmed to hit the lunar surface and cause seismic waves at known
times and distances from seismographic stations.
C They were programmed to land 1,000 kilometers from existing seismographic stations.
D They were programmed to record meteorite activity and send it to seismographic
stations.

The waves recorded by lunar impacts and moonquakes indicated that most of
the Moon is solid rock. The layered crustal shell on the surface is about 60
kilometers thick, and below lies a denser solid mantle about 1,000 kilometers
thick. This overlies a central core that may be somewhat softer than the
mantle but is most probably not liquid. The picture of Earth's interior is
markedly different. Moonquakes themselves differ sharply from earthquakes.
A small earthquake may shake a remote seismograph for a minute or so, but
on the Moon, the recorded shaking of the lunar surface in a moonquake
continues for as much as an hour.
6.The word "markedly" in the passage is closest in meaning to
A relatively
B distinctly
C surprisingly
D seemingly
7.According to paragraph 6, all of the following are true of the Moon EXCEPT:
A The crust of the Moon is more than 1,000 kilometers thick.
B The central core of the Moon is probably softer than the mantle,but not liquid.
C Seismic waves from quakes on the Moon last longer than those from earthquakes.
D The Moon is mostly solid rock.
8.Which of the following best describes the role of paragraph 6 in the passage?
A It summarizes the different ways in which seismic-wave velocities can be studied both
in moonquakes and in earthquakes.
BIt shows how natural and artificial lunar impacts have provided more information about
the Moon's interior than have deep and surface moonquakes
C It illustrates how the studies on travel times of seismic waves on Earth differed from
similar studies conducted on the lunar surface.
D It explains the findings obtained through the studies of quakes and impacts on the
lunar surface.
9.Look at the four squaresthat indicate where the following sentence could be
added to the passage
Many of Earth's geological mechanisms, however, are absent on the Moon.
Where would the sentence best fit？Click on a square sentence to the passage.
10.Seismographic stations were set up on the Moon during the Apollo landings.
Select 3 answers
A Until the lunar program of the United States began, people had many false beliefs
about the causes of moonquakes
B Deep moonquakes occur regularly and seem to be connected to the Moon's position
relative to Earth
C Meteorite and spacecraft impacts produced information on the seismic velocities of
rocks, which in turn helped determine the characteristics of the Moon's interior
D Most moonquakes are very small, with a few larger quakes each year, probably caused
by volcanic activity.
E Surface moonquakes are irregular and, like earthquakes, are thought to be caused by
strain in the crust
F Because the structure of the Moon is different from that of Earth,moonquakes are more
powerful and much shorter than earthquakes

答案：1C 2B 3B 4A 5B 6B 7A 8D 9B 10BCE