本文是及答案解析【Climate of
Venus】，主要包括题目和答案解析的部分，提供手机号可以免费下载更多托福TPO资料，网已经给大家更新到了TPO53套。
Climate of Venus
(原文略)
Paragraph 1
Earth has abundant water in its oceans but very little carbon dioxide in its relatively thin atmosphere. By contrast, Venus is very dry and its thick atmosphere is mostly carbon dioxide. The original atmospheres of both Venus and Earth were derived at least in part from gases spewed forth, or outgassed, by volcanoes. The gases that emanate from present-day volcanoes on Earth, such as Mount Saint Helens, are predominantly water vapor, carbon dioxide, and sulfur dioxide. These gases should therefore have been important parts of the original atmospheres of both Venus and Earth. Much of the water on both planets is also thought to have come from impacts from comets, icy bodies formed in the outer solar system.
1. According to paragraph 1, in what major respect are Venus and Earth different from each other?【事实信息题】
A. Whether carbon dioxide v/as present in their original atmospheres
B. How thin their original atmospheres were
C. What their present-day atmospheres mainly consist of
D. How long ago they first developed an atmosphere
答案：C
解析：从原文前两句话“Earth has abundant water in its oceans but very little carbon dioxide in its relatively thin atmosphere. By contrast, Venus is very dry and its thick atmosphere is mostly carbon dioxide.”可看出，地球大气层含有很少的二氧化碳，而金星的大气层中却含有大量二氧化碳。所以C选项正确，地球和金星的区别就是如今大气层的组成。
2. Why does the author mention "present-day volcanoes on Earth"? 【修辞目的题】
A. To provide an example of an important difference between present-day Venus and present-day Earth
B. To help explain why Earth's atmosphere still contains traces of sulfur dioxide but Venus' does not
C. To indicate one source of information about the likely composition of the original atmospheres of Venus and Earth
D. To account for the fact that Earth’s water supply no longer comes primarily from impacting comets
答案：C
解析：根据原文“These gases should therefore have been important parts of the original atmospheres of both Venus and Earth.”,作者提及"present-day volcanoes on Earth"是为了说明金星和地球原始的大气组成中的sources就是前文说的“water vapor, carbon dioxide, and sulfur dioxide.”，所以C选项正确。
Paragraph 2
In fact, water probably once dominated the Venusian atmosphere. Venus and Earth are similar in size and mass, so Venusian volcanoes may well have outgassed as much water vapor as on Earth, and both planets would have had about the same number of comets strike their surfaces. Studies of how stars evolve suggest that the early Sun was only about 70 percent as luminous as it is now, so the temperature in Venus’ early atmosphere must have been quite a bit lower. Thus water vapor would have been able to liquefy and form oceans on Venus. But if water vapor and carbon dioxide were once so common in the atmospheres of both Earth and Venus, what became of Earth’s carbon dioxide? And what happened to the water on Venus?
3. According to paragraph 2, what is one reason for thinking that at one time, there were significant amounts of water on Venus? 【事实信息题】
A. Because of Venus’ size and mass, its volcanoes probably produced much more water vapor than volcanoes on Earth did.
B. The low temperature of Venus' early atmosphere can be explained only by the presence of water.
C. The presence of carbon dioxide in a planet's atmosphere is an indicator of water on that planet.
D. Venus probably was struck by roughly as many comets as Earth was.
答案：D
解析：根据原文“ and both planets would have had about the same number of comets strike their surfaces.”可看出，金星和地球都被相同数量的彗星撞击过表面，D选项为同意转换，其中the same number of comets对应D选项的as many comets as Earth,所以D选项正确。
4. The word “luminous” in the passage is closest in meaning to 【词汇题】
A. dense
B. bright
C. large
D. active
答案：B
解析：Luminous,意为发光的，明亮的。
Dense,稠密的，浓厚的。Bright,明亮的。Large,大的。Active,积极的，主动的。所以B选项正确。
Paragraph 3
The answer to the first question is that carbon dioxide is still found in abundance on Earth, but now, instead of being in the form of atmospheric carbon dioxide, it is either dissolved in the oceans or chemically bound into carbonate rocks, such as the limestone and marble that formed in the oceans. If Earth became as hot as Venus, much of its carbon dioxide would be boiled out of the oceans and baked out of the crust. Our planet would soon develop a thick, oppressive carbon dioxide atmosphere much like that of Venus.
本文是托福tpo41阅读题目文本及答案解析【Climate of Venus】。
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. 【句子简化题】
A. The first question to be answered is how Earth’s atmospheric carbon dioxide either got dissolved in the oceans or got chemically bound into carbonate rocks.
B. The fact that Earth’s abundant carbon dioxide is more often found in carbonate rock than dissolved in the oceans is the answer to the first question.
C. Earth still has abundant carbon dioxide, but instead of being in the atmosphere it is now dissolved in the oceans or chemically bound into ocean rocks.
D. The formation of limestone and marble used up the carbon dioxide that was dissolved in Earth’s oceans so that only carbon dioxide in atmospheric form remained.
答案：C
解析：Highlighted部分意为，地球上仍有丰富的二氧化碳，但是现在，它们已经不再存在于大气层中，而是或者分解于海洋中，或者以化学形式进入到碳酸盐岩中。只有C选项符合句意，因此C选项正确。
Paragraph 4
To answer the question about Venus’ lack of water, we must return to the early history of the planet. Just as on present-day Earth, the oceans of Venus limited the amount of atmospheric carbon dioxide by dissolving it in the oceans and binding it up in carbonate rocks. But being closer to the Sun than Earth is, enough of the liquid water on Venus would have vaporized to create a thick cover of water vapor clouds. Since water vapor is a greenhouse gas, this humid atmosphere—perhaps denser than Earth’s present-day atmosphere, but far less dense than the atmosphere that envelops Venus today—would have efficiently trapped heat from the Sun. At first, this would have had little effect on the oceans of Venus. Although the temperature would have climbed above 100° C, the boiling point of water at sea level on Earth, the added atmospheric pressure from water vapor would have kept the water in Venus’ oceans in the liquid state.
6. According to paragraph 4, what is one factor that kept the amount of carbon dioxide in the atmosphere of early Venus relatively low? 【事实信息题】
A. The presence of water vapor clouds
B. The presence of oceans
C. Rapidly increasing temperatures at ground level
D. Low atmospheric pressures
答案：B
解析：根据原文“the oceans of Venus limited the amount of atmospheric carbon dioxide by dissolving it in the oceans and binding it up in carbonate rocks.”, 可看出是ocean导致的二氧化碳含量较低。所以B选项正确。
Paragraph 6
Once Venus’ oceans disappeared, so did the mechanism for removing carbon dioxide from the atmosphere. With no oceans to dissolve it, outgassed carbon dioxide began to accumulate in the atmosphere, intensifying the greenhouse effect even more Temperatures eventually became high enough to" bake out” any carbon dioxide that was trapped in carbonate rocks. This liberated carbon dioxide formed the thick atmosphere of present-day Venus. Over time, the rising temperatures would have leveled off, solar ultraviolet radiation having broken down atmospheric water vapor molecules into hydrogen and oxygen. With all the water vapor gone, the greenhouse effect would no longer have accelerated.
7. The phrase “mechanism for” in the passage is closest in meaning to 【词汇题】
A. means of
B. importance of
C. need for
D. benefits of
答案：A
解析：Mechanism for, 意为…的途径。
Means of, 意为…的方法。Importance of, 意为…的重要性。Need for, 意为对于…的需求。Benefits of, 意为…的好处。所以A选项正确。
Paragraph 5
This hot and humid state of affairs may have persisted for several hundred million years. But as the Sun’s energy output slowly increased over time, the temperature at the surface would eventually have risen above 374°C. Above this temperature, no matter what the atmospheric pressure. Venus’ oceans would have begun to evaporate, and the added water vapor in the atmosphere would have increased the greenhouse effect. This would have made the temperature even higher and caused the oceans to evaporate faster, producing more water vapor. That, in turn, would have further intensified the greenhouse effect and made the temperature climb higher still.
8. The word “persisted” in the passage is closest in meaning to 【词汇题】
A. improved
B. continued
C. weakened
D. evolved
答案：B
解析：Persisted, 持续。
Improved, 提高，改进。Continued, 持续，继续。Weakened, 削弱，减弱。Evolved, 发展，进化。所以B选项正确。
9. According to paragraph 5, what happens when temperatures rise above 374°C? 【事实信息题】
A. Atmospheric pressure begins to decrease.
B. Water vapor disappears from the atmosphere.
C. Water evaporates regardless of atmospheric pressure.
D. More energy is required to evaporate a given volume of water.
答案：C
解析：根据原文“Venus’ oceans would have begun to evaporate, and the added water vapor in the atmosphere would have increased the greenhouse effect.”可知，当温度高于374摄氏度时，金星上的海洋会开始蒸发，在大气层中已增加了的水蒸气会加剧温室效应。其中as many comets as Earth对应C选项中的Water evaporates, 所以C选项正确。
Paragraph 6
Once Venus’ oceans disappeared, so did the mechanism for removing carbon dioxide from the atmosphere. With no oceans to dissolve it, outgassed carbon dioxide began to accumulate in the atmosphere, intensifying the greenhouse effect even more Temperatures eventually became high enough to" bake out” any carbon dioxide that was trapped in carbonate rocks. This liberated carbon dioxide formed the thick atmosphere of present-day Venus. Over time, the rising temperatures would have leveled off, solar ultraviolet radiation having broken down atmospheric water vapor molecules into hydrogen and oxygen. With all the water vapor gone, the greenhouse effect would no longer have accelerated.
10. According to paragraph 6, extremely high temperatures increased the amount of carbon dioxide in Venus’ atmosphere by 【事实信息题】
A. increasing the rate which carbon dioxide was outgassed
B. baking out carbon dioxide from carbonate rocks
C. creating additional water vapor
D. replacing the previous mechanisms for removing carbon dioxide with less effective ones
答案：B
解析：题干问，是通过何种方式使得极高的气温增加了金星大气层中二氧化碳含量的。根据原文“intensifying the greenhouse effect even more Temperatures eventually became high enough to" bake out” any carbon dioxide that was trapped in carbonate rocks.”可知，选项B为同义替换，所以B选项正确。
11. The passage supports the idea that the basic reason that Venus and Earth are now so different from each other is that 【事实信息题】
A. early Venus had more frequent volcanic outgassing than early Earth did
B. early Venus had far less liquid water than early Earth did
C. volcanic activity stopped relatively early on Venus but continued on Earth
D. Venus is closer to the Sun than Earth is
答案：D
解析：根据第四段原文“But being closer to the Sun than Earth is, enough of the liquid water on Venus would have vaporized to create a thick cover of water vapor clouds.”可知，由于金星比太阳离地球更近，金星上足够的液体会蒸发形成一层很厚的水蒸气云。这就是金星和地球本质上的区别。其中But being closer to the Sun than Earth is对应D选项的Venus is closer to the Sun than Earth is, 所以选择D选项。
Paragraph 5
12. Look at the four squares [■] that indicate where the following sentence could be added to the passage. 【句子插入题】
This cycle of rising temperatures following an increase in greenhouse gases is known as the
runaway greenhouse effect.
Where would the sentence best fit? Click on a square [■] to add the sentence to the passage.
This hot and humid state of affairs may have persisted for several hundred million years. But as the Sun’s energy output slowly increased over time, the temperature at the surface would eventually have risen above 374°C. [■] Above this temperature, no matter what the atmospheric pressure. Venus’ oceans would have begun to evaporate, and the added water vapor in the atmosphere would have increased the greenhouse effect. [■] This would have made the temperature even higher and caused the oceans to evaporate faster, producing more water vapor. [■] That, in turn, would have further intensified the greenhouse effect and made the temperature climb higher still. [■]
答案：D
解析：根据此段最后一句“That, in turn, would have further intensified the greenhouse effect and made the temperature climb higher still. ”中的“in turn”，即可选择D选项，因为给出的句子中的关键词是“This cycle”，即这个循环。
13. Directions: Select from the seven phrases below the 2 phrases that correctly characterize early Venus and the 3 phrases that correctly characterize present-day Venus. Drag each phrase you select into the appropriate column of the table. Two of the phrases will NOT be used. This question is worth 3 points. 【表格题】
Drag your answer choices to the spaces where they belong. To remove an answer choice, click on it.
To review the passage, click VIEW TEXT.
Early Venus
Present-day Venus
Answer Choices
A. in the atmosphere
B. Carbon dioxide present only in atmospheric form
C. An atmosphere quite similar to that of early Earth
D. Very dense but relatively cool atmosphere
E. Completely covered with water
F. Complete absence of surface water
G. Essentially stable temperatures
答案：
Early Venus：A, C
Present-day Venus: B, E, G
解析：
Early Venus：A, C
A选项，参照原文第二段第一句话“In fact, water probably once dominated the Venusian atmosphere. ”.
C选项，参照原文第二段第二句话“Venus and Earth are similar in size and mass, so Venusian volcanoes may well have outgassed as much water vapor as on Earth. ”.
Present-day Venus: B, E, G
B选项，参照原文第六段第三句话“This liberated carbon dioxide formed the thick atmosphere of present-day Venus. ”.
G选项，参照原文第六段第四句话“Over time, the rising temperatures would have leveled off”.
根据原文第五段第二句话“the temperature at the surface would eventually have risen above 374°C.”可看出金星表面温度很高，已达到了374摄氏度，所以D选项的“relatively cool atmosphere”错误。
根据原文第五段第三句话“Above this temperature, no matter what the atmospheric pressure. Venus’ oceans would have begun to evaporate, and the added water vapor in the atmosphere would have increased the greenhouse effect. ”可知F选项错误，金星表层并非完全缺水。因此选择E选项。
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