Earth hasabundantwater in its oceans but very littlecarbondioxidein itsrelativelythinatmosphere. Bycontrast,Venusis very dry and its thickatmosphereis mostlycarbondioxide. Theoriginalatmospheres of bothVenusand Earth were derived atleastin part from gases spewed forth, or outgassed, by volcanoes. The gases thatemanatefrom present-day volcanoes on Earth, such asMountSaint Helens, arepredominantlywatervapor,carbondioxide, andsulfurdioxide. These gases shouldthereforehave been important parts of theoriginalatmospheres of bothVenusand Earth. Much of the water on both planets is also thought to have come from impacts from comets, icy bodies formed in the outersolarsystem.

In fact, water probably once dominated the Venusianatmosphere. Venusand Earth aresimilarin size andmass, so Venusian volcanoes may well have outgassed as much watervaporas on Earth, and both planets would have had about the same number of cometsstriketheir surfaces. Studies of how starsevolvesuggest that the early Sun was only about 70 percent asluminousas it is now, so thetemperatureinVenus’ earlyatmospheremust have been quite a bitlower. Thus watervaporwould have been able to liquefy and form oceans onVenus. But if watervaporandcarbondioxidewere once socommonin the atmospheres of both Earth andVenus, what became of Earth’scarbondioxide? And what happened to the water onVenus?

The answer to the first question is thatcarbondioxideis still found inabundanceon Earth, but now,insteadof being in the form ofatmosphericcarbondioxide, it is either dissolved in the oceans or chemicallyboundintocarbonaterocks, such as thelimestoneandmarblethat formed in the oceans. If Earth became as hot asVenus, much of itscarbondioxidewould be boiled out of the oceans and baked out of thecrust. Ourplanetwould soon develop a thick, oppressivecarbondioxideatmospheremuch like that ofVenus.

To answer the question aboutVenus’lackof water, we must return to the earlyhistoryof theplanet. Just as on present-day Earth, the oceans ofVenuslimited theamountofatmosphericcarbondioxideby dissolving it in the oceans and binding it up incarbonaterocks. But being closer to the Sun than Earth is, enough of theliquidwater onVenuswould have vaporized to create a thick cover of watervaporclouds. Since watervaporis a greenhouse gas, thishumidatmosphere—perhaps denser than Earth’s present-dayatmosphere, but far lessdensethan theatmospherethat envelopsVenustoday—would have efficiently trapped heat from the Sun. At first, this would have had little effect on the oceans ofVenus. Although thetemperaturewould have climbed above 100° C, the boiling point of water at sealevelon Earth, the addedatmosphericpressurefrom watervaporwould have kept the water inVenus' oceans in theliquidstate.

This hot andhumidstateof affairs may have persisted for several hundred million years. But as the Sun’s energyoutputslowly increased over time, thetemperatureat the surface wouldeventuallyhave risen above 374°C. Above thistemperature, no matter what theatmosphericpressure,Venus’ oceans would have begun toevaporate, and the added watervaporin theatmospherewould have increased the greenhouse effect. This would have made thetemperatureevenhigher and caused the oceans toevaporatefaster, producing more watervapor. That, in turn, would have further intensified the greenhouse effect and made thetemperatureclimb higher still.

OnceVenus’ oceans disappeared, so did themechanismfor removingcarbondioxidefrom theatmosphere. With no oceans todissolveit, outgassedcarbondioxidebegan toaccumulatein theatmosphere, intensifying the greenhouse effectevenmore. Temperatureseventuallybecame high enough to "bakeout" anycarbondioxidethat was trapped incarbonaterocks. This liberatedcarbondioxideformed the thickatmosphereof present-dayVenus. Over time, the rising temperatures would have leveled off,solarultravioletradiationhaving broken downatmosphericwatervapormolecules intohydrogenandoxygen. With all the watervaporgone, the greenhouse effect would no longer haveaccelerated.

Questions:
question_stem: According to paragraph 1, in what major respect are Venus and Earth different from each other?
choices: tag: A
text: Whether carbon dioxide was present in their original atmospheres

tag: B
text: How thin their original atmospheres were

tag: C
text: What their present-day atmospheres mainly consist of

tag: D
text: How long ago they first developed an atmosphere
answer_key: C
explanation: 【题目翻译】根据第1段，金星和地球在哪些主要方面不同？
A：原始大气中是否存在二氧化碳

B：原来的大气层有多薄

C：它们现在的大气主要由什么组成？

D：多久前它们第一次形成大气层

【判定题型】：题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】根据 Passage 1，原句为“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.”，意思是“地球的海洋中有丰富的水，但相对稀薄的大气中却很少有二氧化碳。相比之下，金星非常干燥，其厚厚的大气层主要是二氧化碳。”。

【逻辑分析】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。

【选项分析】
A.都是含有二氧化碳的，只是含量不同。故错误。
B.金星的大气是很厚的。故错误。
C.C 选项正确，地球和金星的区别就是如今大气层的组成。
D.文章未提及，故错误。

question_stem: Why does the author mention "present-day volcanoes on Earth"?
choices: tag: A
text: To provide an example of an important difference between present-day Venus and present-day Earth

tag: B
text: To help explain why Earth's atmosphere still contains traces of sulfur dioxide but Venus' does not

tag: C
text: To indicate one source of information about the likely composition of the original atmospheres of Venus and Earth

tag: D
text: To account for the fact that Earth’s water supply no longer comes primarily from impacting comets
answer_key: C
explanation: 【题目翻译】为什么作者提到“地球上的现今火山”？
A：举例说明今天的金星和现在的地球之间的一个重要区别。

B：有助于解释为什么地球大气中仍然含有二氧化硫，而金星却没有。

C：表示一个有关金星和地球原始大气成分的信息来源。

D：考虑到地球的水供应不再主要来自撞击彗星这一事实。

【判定题型】：根据题干问法“why …… mention”，题目询问“xxxxxx”(文章引用内容)的修辞目的，可以判断本题为修辞目的题。

【关键词定位】根据关键词“present-day volcanoes”,定位到 Passage 1 第5句，原句为“These gases should therefore have been important parts of the original atmospheres of both Venus and Earth.”。


【引用内容分析】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。

【选项分析】
A.不是要说明区别，是要说明大气成分。故错误。
B.不单单是二氧化硫，而是大气成分。故错误。
C.选项就是前文说的“water vapor, carbon dioxide, and sulfur dioxide”，所以 C 选项正确。
D.主题不对，与水供应无关。故错误。

question_stem: According to paragraph 2, what is one reason for thinking that at one time, there were significant amounts of water on Venus?
choices: tag: A
text: Because of Venus’ size and mass, its volcanoes probably produced much more water vapor than volcanoes on Earth did.

tag: B
text: The low temperature of Venus' early atmosphere can be explained only by the presence of water.

tag: C
text: The presence of carbon dioxide in a planet's atmosphere is an indicator of water on that planet.

tag: D
text: Venus probably was struck by roughly as many comets as Earth was.
answer_key: D
explanation: 【题目翻译】根据第2段，有什么理由认为金星上曾经有大量的水？
A：由于金星的大小和质量，它的火山可能产生比地球上的火山更多的水蒸气。

B：金星早期大气的低温只能用水来解释。

C：在一个行星的大气层中，二氧化碳的存在是该行星上水分的一个指标。

D：金星可能受到的彗星数量和地球差不多。

【判定题型】：题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】根据关键词“water on Venus”,定位到 Passage 2，原句为“and both planets would have had about the same number of comets strike their surfaces.”，意思是“两颗行星的彗星撞击其表面的数量差不多”。

【逻辑分析】金星和地球都被相同数量的彗星撞击过表面。

【选项分析】
A.文章说：两个星球的火山排出的水蒸气可能是一样多的。故错误。
B.金星早期大气的低温是和太阳亮度有关。故选项错误。
C.文章未说二氧化碳可以是一个指标。故错误。
D.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。

question_stem: The word “luminous” in the passage is closest in meaning to
choices: tag: A
text: dense

tag: B
text: bright

tag: C
text: large

tag: D
text: active
answer_key: B
explanation: 【题目翻译】段落中的“luminous”一词最接近于下列哪个选项？
A：稠密的
B：光明的
C：大的
D：积极的

【判定题型】：题目要求选出与高亮单词意思最接近的选项，故判断本题为词汇题。

【关键词定位】：根据关键词“luminous”,定位到原句“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. ”。

【词汇解析】：词汇“luminous”的意思是“发光的，明亮的”,带入到原句中，原句的意思是“对恒星如何进化的研究表明，早期的太阳光只有现在的70%左右，所以金星早期大气层的温度一定要低一些。”。

【选项分析】
A：稠密的。不符，错误

B：光明的。同义替换，正确

C：大的。不符，错误

D：积极的。不符，错误

question_stem: 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
choices: tag: A
text: 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.

tag: B
text: 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.

tag: C
text: 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.

tag: D
text: 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.
answer_key: C
explanation: 【题目翻译】下面哪句话最能表达文章中突出显示的句子中的基本信息？错误的选择会以重要的方式改变意义，或遗漏重要信息。
A：首先要回答的问题是，地球大气中的二氧化碳是如何溶解在海洋中，或是化学结合到碳酸盐岩中的。
B：事实上，地球上丰富的二氧化碳更多地存在于碳酸盐岩中，而不是溶解在海洋中，这是第一个问题的答案。
C：地球上仍然有丰富的二氧化碳，但现在它不在大气中，而是溶解在海洋中或化学结合到海洋岩石中。
D：石灰岩和大理石的形成耗尽了溶解在地球海洋中的二氧化碳，所以只有大气形式的二氧化碳残留。

【判定题型】：根据题目问法，题目要求选择和高亮句意思逻辑都最为接近的句子，故判断本题为句子简化题。

【句子分析】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。

【选项分析】
A.溶解方式不是重点。故错误。
B.溶解在海洋中也是有的。故选项错误。
C.C 选项符合句意，因此 C 选项正确。
D.原句未提到石灰和大理石。故错误。

question_stem: According to paragraph 4, what is one factor that kept the amount of carbon dioxide in the atmosphere of early Venus relatively low?
choices: tag: A
text: The presence of water vapor clouds

tag: B
text: The presence of oceans

tag: C
text: Rapidly increasing temperatures at ground level

tag: D
text: Low atmospheric pressures
answer_key: B
explanation: 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。

question_stem: The phrase “mechanism for” in the passage is closest in meaning to
choices: tag: A
text: means of

tag: B
text: importance of

tag: C
text: need for

tag: D
text: benefits of
answer_key: A
explanation: 【题目翻译】段落中的“mechanism for”一词最接近于下列哪个选项？
A：Means of, 意为…的方法。
B：Importance of, 意为…的重要性。
C：Need for, 意为对于…的需求。
D：Benefits of, 意为…的好处。

【判定题型】：题目要求选出与高亮单词意思最接近的选项，故判断本题为词汇题。

【关键词定位】：根据关键词“mechanism for”,定位到原句“Once Venus’ oceans disappeared, so did the mechanism for removing carbon dioxide from the atmosphere.”。

【词汇解析】：词汇“mechanism for”的意思是“意为…的途径”,带入到原句中，原句的意思是“一旦金星的海洋消失，从大气中去除二氧化碳的机制也随之消失”。

【选项分析】
A：Means of, 意为…的方法。同义替换，正确
B：Importance of, 意为…的重要性。不符，错误
C：Need for, 意为对于…的需求。不符，错误
D：Benefits of, 意为…的好处。不符，错误

question_stem: The word “persisted” in the passage is closest in meaning to
choices: tag: A
text: improved

tag: B
text: continued

tag: C
text: weakened

tag: D
text: evolved
answer_key: B
explanation: 【题目翻译】段落中的“persisted”一词最接近于下列哪个选项？
A：Improved, 提高，改进。
B：Continued, 持续，继续。
C：Weakened, 削弱，减弱。
D：Evolved, 发展，进化。

【判定题型】：题目要求选出与高亮单词意思最接近的选项，故判断本题为词汇题。

【关键词定位】：根据关键词“persisted”,定位到原句“This hot and humid state of affairs may have persisted for several hundred million years. ”。

【词汇解析】：词汇“persisted”的意思是“持续”,带入到原句中，原句的意思是“这种湿热的状态可能持续了几亿年”。

【选项分析】
A：Improved, 提高，改进。不符，错误
B：Continued, 持续，继续。同义替换，正确
C：Weakened, 削弱，减弱。不符，错误
D：Evolved, 发展，进化。不符，错误

question_stem: According to paragraph 5, what happens when temperatures rise above 374°C?
choices: tag: A
text: Atmospheric pressure begins to decrease.

tag: B
text: Water vapor disappears from the atmosphere.

tag: C
text: Water evaporates regardless of atmospheric pressure.

tag: D
text: More energy is required to evaporate a given volume of water.
answer_key: C
explanation: 【题目翻译】根据第5段，当温度上升到374°C 以上时会发生什么？
A：大气压开始下降。

B：水蒸气从大气中消失。

C：不管大气压如何，水都会蒸发。

D：蒸发一定体积的水需要更多的能量。

【判定题型】：题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】：根据关键词“above 374°C”,定位到 Passage5，原句为“Venus’ oceans would have begun to evaporate, and the added water vapor in the atmosphere would have increased the greenhouse effect.”，意思是“金星的海洋会开始蒸发，大气中增加的水蒸气会增加温室效应”。

【逻辑分析】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。

【选项分析】
A.未提到大气压如何变化，故错误。
B.会产生更多的水蒸气。故错误。
C.文章中 as many comets as Earth 对应 C 选项中的 Water evaporates, 所以 C 选项正确。
D.未提及是否需要更多的能量。故错误。

question_stem: According to paragraph 6, extremely high temperatures increased the amount of carbon dioxide in Venus’ atmosphere by
choices: tag: A
text: increasing the rate which carbon dioxide was outgassed

tag: B
text: baking out carbon dioxide from carbonate rocks

tag: C
text: creating additional water vapor

tag: D
text: replacing the previous mechanisms for removing carbon dioxide with less effective ones
answer_key: B
explanation: 【题目翻译】根据第6段，极高的温度通过什么使金星大气中的二氧化碳含量增加了
A：提高二氧化碳的脱气率

B：从碳酸盐岩中烘焙出二氧化碳

C：产生额外的水蒸气

D：用效率较低的机制取代以前的二氧化碳去除机制

【判定题型】：题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】：根据关键词“extremely high temperatures”,定位到 Passage6，原句为“intensifying the greenhouse effect even more Temperatures eventually became high enough to" bake out” any carbon dioxide that was trapped in carbonate rocks.”，意思是“温室效应的加剧，甚至更多的温度最终变得足够高，足以“烘烤”任何被困在碳酸盐岩中的二氧化碳。”。

【逻辑分析】温室效应可以“烘烤”二氧化碳。

【选项分析】
A.是“烤出”碳酸盐岩中的二氧化碳。故选项错误。
B.B 为同义替换，所以 B 选项正确。
C.是从碳酸盐岩中烘焙出二氧化碳，不是产生额外的水蒸气。故错误。
D.不符文意，故错误。

question_stem: The passage supports the idea that the basic reason that Venus and Earth are now so different from each other is that
choices: tag: A
text: early Venus had more frequent volcanic outgassing than early Earth did

tag: B
text: early Venus had far less liquid water than early Earth did

tag: C
text: volcanic activity stopped relatively early on Venus but continued on Earth

tag: D
text: Venus is closer to the Sun than Earth is
answer_key: D
explanation: 【题目翻译】这篇文章支持这样的观点：金星和地球现在如此不同的基本原因是
A：早期的金星比早期的地球有更频繁的火山喷发。

B：早期的金星比早期的地球有更少的液态水。

C：火山活动在金星上停止得比较早，但在地球上继续。

D：金星比地球更接近太阳

【判定题型】：题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】：根据关键词“different from each other”,定位到 Passage 4，原句为“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.”，意思是“但是由于离太阳比地球更近，金星上足够多的液态水会蒸发，形成一层厚厚的水蒸气云。”。

【逻辑分析】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。

【选项分析】
A.文章未提及，故错误。
B.文章未提及，故错误。
C.文章未提及，故错误。
D.原文中 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。