The creation of life requires a set of chemical elements for making thecomponentsof cells. Life on Earth uses about 25 of the 92 naturally occurring chemical elements, although just 4 of these elements—oxygen,carbon,hydrogen, andnitrogen—make up about 96 percent of themassof living organisms. Thus, a first requirement for life might be the presence of most or all of the elements used by life.

Interestingly, this requirement can probably be met by almost any world. Scientists havedeterminedthat all chemical elements in theuniversebesideshydrogenandhelium(and atraceamountoflithium) were produced by stars. These are known as heavy elements because they are heavier thanhydrogenandhelium. Although all of these heavy elements are quiterarecompared tohydrogenandhelium, they are found just about everywhere.

Heavy elements are continually being manufactured by stars and released into space bystellardeaths, so theiramountcompared tohydrogenandheliumgraduallyrises with time. Heavy elements make up about 2 percent of the chemicalcontent(bymass) of oursolarsystem, the other 98 percent ishydrogenandhelium. In some very old star systems, which formed before many heavy elements were produced, the heavy-element share may be less than 0.1 percent. Nevertheless, every star system studied has atleastsomeamountof all the elements used by life. Moreover, when planetesimals—small,solidobjects formed in the earlysolarsystem that mayaccumulateto become planets—condensewithin a forming star system, they areinevitablymade from heavy elements because the morecommonhydrogenandheliumremaingaseous. Thus, planetesimals everywhere shouldcontainthe elements needed for life, which means that objects built from planetesimals—planets, moons, asteroids, and comets-alsocontainthese elements. The nature of solar-systemformationexplains why Earth contains all the elements needed for life, and it is why weexpectthese elements to be present on other worldsthroughoutoursolarsystem,galaxy, anduniverse.

Note that thisargumentdoes not change,evenif we allow for life very different from life on Earth. Life on Earth iscarbonbased, and most biologists believe that life elsewhere is likely to becarbonbased as well. However, we cannotabsolutelyrule out the possibility of life with another chemical basis, such assiliconornitrogen. The set of elements (or theirrelativeproportions) used by life based on some otherelementmight besomewhatdifferent from that used by carbon-based life on Earth. But the elements are still products of stars and would still be present in planetesimals everywhere. No matter what kinds of life we are looking for, we are likely to find the necessary elements on almost everyplanet, moon,asteroid, andcometin theuniverse.

Asomewhatstricter requirement is the presence of these elements in molecules that can be used as ready-made building blocks for life, just as early Earth probably had anorganicsoup ofaminoacids and othercomplexmolecules. Earth'sorganicmolecules likely came from somecombinationof three sources: chemical reactions in theatmosphere, chemical reactions near deep-sea vents in the oceans, and molecules carried to Earth by asteroids and comets. The first two sources canoccuronly on worlds with atmospheres or oceans,respectively. But the thirdsourceshould have broughtsimilarmolecules to nearly all worlds in oursolarsystem.

Studies of meteorites and comets suggest thatorganicmolecules arewidespreadamong both asteroids and comets. Because each body in thesolarsystem was repeatedly struck by asteroids and comets during the period known as the heavybombardment(about 4 billion years ago), each body should have received atleastsomeorganicmolecules. However, these moleculestendto be destroyed bysolarradiationon surfaces unprotected by atmospheres. Moreover, while these molecules might stayintactbeneaththe surface (as they evidently do on asteroids and comets), they probably cannot react with each other unless some kind ofliquidor gas isavailableto move them about. Thus, if we limit our search to worlds on whichorganicmolecules are likely to be involved in chemical reactions, we can probably rule out any world that lacks both anatmosphereand a surface orsubsurfaceliquidmedium, such as water.

Questions:
question_stem: The word "components" in the passage is closest in meaning to
choices: tag: A
text: parts

tag: B
text: bodies

tag: C
text: combinations

tag: D
text: characteristics
answer_key: A
explanation: 【题目翻译】与文中单词“components”意思最为相近的单词是？
A 选项“parts”意思是“部分、片段、组成”
B 选项“bodies”意思是“身体、主体、主要部分” 
C 选项“combinations”意思是“结合，组合”
D 选项“characteristics”意思是“特点、特性”

【判断题型】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】它所在的句子“The creation of life requires a set of chemical elements for making the components of cells.”

【词汇解析】“part”的意思是“部分、片段、组成”，所在句子的意思是“生命的创造需要一套用于制造细胞成分的化学元素”。

【选项分析】
A 选项“parts”意思是“部分、片段、组成”，意思最为贴切，故正确。
B 选项“bodies”意思是“身体、主体、主要部分”,代入可知，句意不符，排除。 
C 选项“combinations”意思是“结合，组合”，代入可知，句意不符，排除。 
D 选项“characteristics”意思是“特点、特性”,代入可知，句意不符，排除。
其中“component”的意思为“成分、组件”，根据同义转换，可知答案为 A。

question_stem: According to paragraphs 1 and 2, living cells contain which of the following?
choices: tag: A
text: All chemical elements in the universe except lithium

tag: B
text: About 25 different elements

tag: C
text: About 96 percent of all known elements

tag: D
text: Ninety-two naturally occurring elements
answer_key: B
explanation: 【题目翻译】根据第一段和第二段，活细胞包含下列哪一种？
A：宇宙中所有化学元素，除了锂
B：大约25种不同的元素
C：所有已知元素的96%左右
D：92种天然元素

【判断题型】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】定位于 The creation of life requires a set of chemical elements for making the components of cells. Life on Earth uses about 25 of the 92 naturally occurring chemical elements.

【逻辑分析】根据文章第一段，可以直接找到表现出答案的一句话：地球上的生命”使用了92种天然化学元素中的25种。

【选项分析】
A 选项的意思为：宇宙中除了锂以外的化学元素，A 项的干扰因素来自于“Scientists have determined that all chemical elements in the universe besides hydrogen and helium (and a trace amount of lithium) were produced by stars”，这里只是说“科学家们已经确定，除了氢和氦（以及微量的锂）之外，宇宙中的所有化学元素都是由恒星产生的”，并没有说生命细胞是由除了锂以外的化学元素组成的，则 A 选项不正确。
B 选项的意思为：大约有25种不同的元素，“地球上的生命”使用了92种天然化学元素中的25种”。地球上的生命是由细胞组成的，则可知生命的细胞的组成部分包括大概25种不同的元素，则 B 项正确。  
C 选项的意思为：大概96%的已知元素，C 选项的干扰因素来自于“although just 4 of these elements—oxygen, carbon, hydrogen, and nitrogen—make up about 96 percent of the mass of living organisms”，意思为“尽管这些元素中只有4种：氧，碳，氢和氮 - 构成了大约96％的活生物体，”这里强调的是生物体的绝大部分都是由氧，碳，氢和氮4种元素组成的，但是不是说所有的细胞都是只由我们知道的元素中的96%组成的，则 C 项不正确。
D 选项的意思为：92种已经存在的元素。D 项的干扰因素来自于“Life on Earth uses about 25 of the 92 naturally occurring chemical elements”，这个应该注意到是92种中的25种，“of”说明并不是全部，则 D 项不正确。

question_stem: Why does the author provide the information that "Heavy elements are continually being manufactured by stars and released into space by stellar deaths"?
choices: tag: A
text: To explain how it is that the elements required for life can be found everywhere.

tag: B
text: To provide evidence that our solar system is relatively young.

tag: C
text: To argue that some solar systems are more likely to support life than others.

tag: D
text: To explain why heavy elements have greater mass than hydrogen and helium.
answer_key: A
explanation: 【题目翻译】为什么作者提供“重元素不断由恒星制造并通过恒星死亡释放到太空”的信息？
A：为了解释为什么生命所需的元素到处都能找到。
B：为证明我们的太阳系相对年轻提供证据。
C：认为一些太阳系比其他太阳系更有可能维持生命。
D：解释为什么重元素的质量比氢和氦大。

【判断题型】根据题干问法“why ……”题目询问“the information”的作的修辞目的，可以判断本题为修辞目的题。

【关键词定位】定位点为“Heavy elements are continually being manufactured by stars and released into space by stellar deaths, so their amount compared to hydrogen and helium gradually rises with time”。

【引用内容分析】本题的出题点为“Heavy elements are continually being manufactured by stars and released into space by stellar deaths, so their amount compared to hydrogen and helium gradually rises with time”，意思就是说“重元素不断由恒星制造并通过恒星死亡释放到太空中，因此它们的量与氢和氦相比随着时间的推移逐渐增加”再根据前文的一句“尽管与氢和氦相比，所有这些重元素都很罕见，但它们几乎遍布各处。”

【选项分析】
A 项中，重元素被释放到太空，即是生命所需的元素到处都能找到的原因，所以 A 项正确。
B 项中，本文的中心是宇宙中生命细胞的组成成分，并不是太阳系的生命长短，则 B 选项与文章的主旨不符，则 B 项不正确。 
C 项的意思为：为了证实一些太阳系比其他的星系更有可能存在生命，C 项中，虽然在第三自然段能够推理出为什么太阳系中能够存在生命，但是其中并没有将太阳系与其他的星系相比较，没有比较关系，所以也就得不出这样的结论，则 C 项不正确。 
D 项的意思为：为了解释为什么重元素比氢和氦的质量更大，D 项中，第三自然段并没有解释为什么重元素比氢和氦的质量更大，属于无中生有的现象，则 D 项不正确。

question_stem: Paragraph 3 suggests that which of the following may be a difference between very old star systems and newer star systems?
choices: tag: A
text: Older star systems are likely to have fewer planets, moons, asteroids, and comets than newer star systems.

tag: B
text: Newer star systems probably contain more hydrogen and helium than older star systems.

tag: C
text: Newer star systems probably contain more heavy elements than older star systems.

tag: D
text: The process of solar-system formation may have been fundamentally different in older star systems than in newer star systems.
answer_key: C
explanation: 【题目翻译】第3段建议下列哪一个可能是非常旧的恒星系统和较新的恒星系统之间的区别？
A：较老的恒星系统比较新的恒星系统有更少的行星、卫星、小行星和彗星。
B：新星系可能比老星系含有更多的氢和氦。
C：新星系可能比老星系含有更多的重元素。
D：在老恒星系统中，太阳系的形成过程可能与新恒星系统有着根本的不同。

【判断题型】根据题干中出现的关键词“suggest”，判定本题为推理题。

【关键词定位】定位于：In some very old star systems, which formed before many heavy elements were produced, the heavy-element share may be less than 0.1 percent.

【逻辑分析】根据定位句可知：在一些非常古老的恒星系统中，这些恒星系统在许多重元素出现之前形成，重元素份额可能低于0.1％。所以可以推断出来老星系中所含的重元素较少。

【选项分析】
A 选项的意思为：老的星系比新的星系可能拥有更少的行星、月亮、小行星以及彗星，A 选项的干扰点来源于“Thus, planetesimals everywhere should contain the elements needed for life, which means that objects built from planetesimals—planets, moons, asteroids, and comets-also contain these elements”，就是说“因此，任何地方的星子都应该包含生命所需要的元素，这意味着由平行星 、行星、卫星、小行星和彗星等构成的物体也包含这些元素”，说明的是其他星系的组成部分，而不是将新的星系与老的星系之间进行比较，则 A 项不正确。 
B 选项的意思为：新的星系比老的星系可能包含更多的氢和氦元素，B 选项，这个选项属于偷换概念，是将正确选项中的“heavy elements”换成了“hydrogen and helium”，而氢和氦并不属于重元素的范畴，则 B 选项不正确。 
C 项的意思是：新星系比老星系所含的重元素要多。符合文章意思，C 项正确。
D 选项的意思为：老的星系中的太阳系的形成过程与新的星系的形成过程可能有着本质的不同。 D 选项，第三自然段并没有说明星系的形成过程，更没有将新的星系与旧的星系的形成过程进行比较，则 D 项不正确。

question_stem: The word "Nevertheless" in the passage is closest in meaning to
choices: tag: A
text: additionally

tag: B
text: however

tag: C
text: in particular

tag: D
text: on the contrary
answer_key: B
explanation: 【题目翻译】与文中单词“Nevertheless”意思最相近的是？
A 选项的意思为：另外，加之 
B 选项的意思为：然而，但是
C 选项的意思为：尤其是
D 选项的意思为：反之

【判断题型】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】Nevertheless, every star system studied has at least some amount of all the elements used by life.

【词汇解析】“Nevertheless”的意思为“然而、不过、虽然如此”，表示转折。

【选项分析】
A 选项的意思为：另外，加之，表示顺承； 不符合。
B 选项的意思为：然而，但是，表示转折； 符合题意，B 项正确。
C 选项的意思为：尤其是，表示强调； 不符合。
D 选项的意思为：反之，指意思相反，表示对立面。 不符合。
则 A、C、D 三项均不符合要求。

question_stem: The word "inevitably" in the passage is closest in meaning to
choices: tag: A
text: typically

tag: B
text: unsurprisingly

tag: C
text: necessarily

tag: D
text: naturally
answer_key: C
explanation: 【题目翻译】与文中单词“inevitably”意思最相近的是？
A 选项的意思为：一般情况下，一般地
B 选项的意思为：意料之中地 
C 选项的意思为：必然地、不可避免地
D 选项的意思为：自然地

【判断题型】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】原文中出现在“they are inevitably made from heavy elements ”

【词汇解析】“inevitably”意思为“必将，不可避免的”，原文中出现在“they are inevitably made from heavy elements ”，意思就是说“它们不可避免地由重元素制成”。

【选项分析】
A 选项的意思为：一般情况下，一般地； 
B 选项的意思为：意料之中地 
C 选项的意思为：一定地、不可避免地； 
D 选项的意思为：自然地。 
则 A、B、D 三项均不符合要求。

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: Planetesimals may remain in star systems when hydrogen and helium combine with less common heavier elements.

tag: B
text: Planetesimals are composed of heavy elements because hydrogen and helium stay in the form of gases.

tag: C
text: Planetesimals are small, solid objects that condense within a forming star system and may become planets.

tag: D
text: When planetesimals accumulate to form planets, they inevitably contain gaseous as well as heavy elements.
answer_key: B
explanation: 【题目翻译】下面哪个句子最能表达文章中突出句子的基本信息？不正确的选择会以重要方式改变含义，或者漏掉必要的信息。
A：当氢气和氦气与不太常见的重元素结合时，小行星可能留在恒星系统中。
B：因为氢和氦以气体的形式存在，所以行星是由重元素组成的。
C：小行星是小而坚固的物体，在形成的恒星系统中凝聚，可能成为行星。
D：当小行星积累形成行星时，它们不可避免地含有气体和重元素。

【判断题型】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】文中划出的句子的意思为“而且，当太阳系中早期太阳系中形成的可能积聚成行星的固体物体在形成恒星系统内凝聚时，它们不可避勉地由重元素制成，因为更常见的氢和氦气保持气态”。

【选项分析】
A 选项的意思为：当氢和氦与较不常见的较重元素结合时，平面星系可能保留在星系中；意思和原句不符合，且因果关系缺失。 
B 选项的意思为：星系由重元素组成，因为氢和氦以气体的形式存在；意思符合，逻辑也正确。 
C 选项的意思为：星系是小而坚固的物体，凝聚在形成的恒星系统内，并可能成为行星；意思和原句不符合，且因果关系缺失。 
D 选项的意思为：当小行星积聚形成行星时，它们不可避免地含有气体和重元素。原句中 because 后面的重要信息缺失。 
将 A、B、C、D 选项进行比较，得出 A、C、D 三项均不符合要求。

question_stem: According to paragraph 4, which of the following is true about possible life on other planets?
choices: tag: A
text: It cannot be based on silicon or nitrogen.

tag: B
text: It could not survive on Earth.

tag: C
text: It probably would not be made of elements produced by stars.

tag: D
text: It is likely to have carbon as its chemical basis.
answer_key: D
explanation: 【题目翻译】根据第4段，关于其他行星上可能的生命，下列哪个是正确的？
A 它不能以硅或氮为基础。
B 它在地球上不能生存。
C 它可能不是由恒星产生的元素构成的。
D 它很可能以碳作为化学基础。

【判断题型】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】第4段。

【逻辑分析】由“ Life on Earth is carbon based, and most biologists believe that life elsewhere is likely to be carbon based as well”可知“地球上的生命是以碳为基础的，大多数生物学家认为其他地方的生活也可能以碳为基础”。

【选项分析】
A 选项的意思为：它不能基于硅或氮；A 项中的干扰点为“However, we cannot absolutely rule out the possibility of life with another chemical basis, such as silicon or nitrogen”，意思为“但是，我们不能完全排除使用另一种化学基础如硅或氮的生命的可能性”，则 A 项不正确； 
B 选项的意思为：它不能在地球上存活；B 项，文章并没有提到它们是否能够在地球上存活，则 B 项是不正确的； 
C 选项的意思为：它不可能由星球产生的元素组成；C 项中的干扰点为“But the elements are still products of stars and would still be present in planetesimals everywhere”，意思为“但这些元素仍然是恒星的产物，并且仍然会以各种行星的形式出现”，则 C 选项不正确。 
D 选项的意思为：它可能是以碳元素为它的化学基础。

question_stem: According to paragraph 5, all of the following are true of the organic molecules on early Earth EXCEPT:
choices: tag: A
text: Some of them were probably brought to Earth by asteroids or comets.

tag: B
text: Some of them probably formed in the atmosphere and oceans.

tag: C
text: They were probably significantly different from the organic molecules present on other planets in the solar system.

tag: D
text: They included complex molecules.
answer_key: C
explanation: 【题目翻译】根据第5段，以下关于地球早期的有机分子，除了哪个以外以下所有情况均属实？
A：其中一些可能是由小行星或彗星带到地球的。
B：有些可能形成于大气和海洋中。
C：它们可能与太阳系其他行星上的有机分子有很大不同。
D：它们包括复杂的分子。

【判断题型】根据题干中出现的大写“EXCEPT”/"NOT" 等其他明显表示否定的词，可以判定本题为否定事实信息题，需要找出与原文信息不符的那个答案。

【关键词定位】Earth's organic molecules likely came from some combination of three sources: chemical reactions in the atmosphere, chemical reactions near deep-sea vents in the oceans, and molecules carried to Earth by asteroids and comets。

【选项分析】
A 选项和 B 选项可以由“Earth's organic molecules likely came from some combination of three sources: chemical reactions in the atmosphere, chemical reactions near deep-sea vents in the oceans, and molecules carried to Earth by asteroids and comets”地球的有机分子可能来自三种来源的某一种组合：大气中的化学反应，海洋深海通风口附近的化学反应以及小行星和彗星携带到地球的分子，得知是正确的。
D 选项可由第一句“A somewhat stricter requirement is the presence of these elements in molecules that can be used as ready-made building blocks for life, just as early Earth probably had an organic soup of amino acids and other complex molecules”得知是正确的。 
综上所述，通过排除法，可得答案为 C。

question_stem: The phrase “widespread among” is closest in meaning to
choices: tag: A
text: frequently present in

tag: B
text: widely separated in

tag: C
text: a significant part of

tag: D
text: found throughout the bodies of
answer_key: A
explanation: 【题目翻译】与文中词组“widespread among”意思最相近的是？
A 选项的意思为：经常出现在； 
B 选项的意思为：被远远分开； 
C 选项的意思为：很重要的部分； 
D 选项的意思为：在整个星体中被发现。 

【判断题型】题目要求选出与高亮词组意思最接近的选项，故判断本题为词汇题。

【关键词定位】Studies of meteorites and comets suggest that organic molecules are widespread among both asteroids and comets. 对陨石和彗星的研究表明，有机分子普遍分布在小行星和彗星中间。

【词汇解析】“widespread among”的意思为“普遍分布于”。

【选项分析】
A 选项“经常出现在”，强调了密集度，和原词“widespread among”在句中意思可以相互替换，故正确。
B 选项“被远远分开”，原词没有强调距离感，故排除； 
C 选项“很重要的部分”，也是无中生有，和原词意思不相关； 
D 选项“在整个星体中被发现”，但没有强调分布情况的密集度，所以不如 A 选项确切，故排除。

question_stem: The word "intact" in the passage is closest in meaning to
choices: tag: A
text: buried

tag: B
text: whole

tag: C
text: confined

tag: D
text: active
answer_key: B
explanation: 【题目翻译】与文中单词“intact”意思最相近的是？
A 选项的意思为：隐藏的，埋于地下的； 
B 选项的意思为：整个的额，整体的； 
C 选项的意思为：受限的，限制的； 
D 选项的意思为：积极的，有活力的。 

【判断题型】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】Moreover, while these molecules might stay intact beneath the surface (as they evidently do on asteroids and comets), they probably cannot react with each other unless some kind of liquid or gas is available to move them about. 

【词汇解析】“intact”的意思为“完整的”，强调整体性。

【选项分析】
A 选项的意思为：隐藏的，埋于地下的； 
B 选项的意思为：整个的额，整体的； 
C 选项的意思为：受限的，限制的； 
D 选项的意思为：积极的，有活力的。 
比较 A、B、C、D 选项的意思，可得 A、C、D 选项均不符合要求，与 B 选项中的“whole”意思接近，则 B 选项正确。

question_stem: According to paragraph 6, why is life unlikely to be found on any planet that lacks both an atmosphere and a surface or subsurface liquid medium?
choices: tag: A
text: Organic molecules must be protected from solar radiation by a surface layer of liquid.

tag: B
text: Planets that lack both of these features are probably too small to have been hit by many asteroids or comets carrying organic matter.

tag: C
text: Organic molecules need a liquid or gaseous environment to bring them together so they can interact.

tag: D
text: An atmosphere is needed to protect organic molecules from being destroyed by asteroids and comets.
answer_key: C
explanation: 【题目翻译】根据第6段，为什么在既缺乏大气层，又缺乏表面或地下液体介质的任何行星上都不可能发现生命？
A：有机分子必须用液体表面层来防止太阳辐射。
B：缺乏这两种特征的行星可能太小了，不能被携带有机物质的许多小行星或彗星击中。
C：有机分子需要液体或气体环境使它们结合在一起，这样它们才能相互作用。
D：需要大气层来保护有机分子免受小行星和彗星的破坏。

【判断题型】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】Each body should have received at least some organic molecules. However, these molecules tend to be destroyed by solar radiation on surfaces unprotected by atmospheres. Moreover, while these molecules might stay intact beneath the surface (as they evidently do on asteroids and comets), they probably cannot react with each other unless some kind of liquid or gas is available to move them about。

【逻辑分析】根据定位句分析，每个个体至少应该接受一些有机分子。 然而，这些分子往往被不受大气保护的表面上的太阳辐射破坏。此外，尽管这些分子可能会在表面下保持完整（因为它们明显对小行星和彗星有影响），但除非某种液体或气体可用于移动它们，否则它们可能无法相互反应”，即气体和液体的环境，对于有机分子的合成是非常重要的。

【选项分析】
A 选项的意思为：有机分子必须由液体层的表面保护其不受太阳射线的辐射； A 选项虽然说法正确，但是，题目问的是“为什么在缺少大气层和液体介质的行星上不可能发现生命？”显然，答非所问，则 A 项不正确；
B 选项的意思为：不具备这两个特点的行星有可能因为太小以至于会被带有有机物质的陨石和彗星所击中； B 选项，第六自然段并没有提到相关的观点，属于无中生有，则 B 项不正确； 
C 选项的意思为：有机分子需要有一个液体或者气体环境，使得它们能够相互反应； C 项正确。
D 选项的意思为：对于保护有机分子不被陨石或者彗星所损坏来说大气层是非常重要的。 由“ these molecules tend to be destroyed by solar radiation on surfaces unprotected by atmospheres”可知，有机分子会收到太阳射线的损坏，并不是陨石和彗星。 D 项也不正确。