『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 54 Passage 3阅读练习：Look at the four squares  that indicate where the following sentence could be added to the passage. To answer the question “Could life exist on other planets?” we must first look at the necessary preconditions for life.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.真题题目及答案解析，TPO/Official 54 Passage 3阅读原文范文音频翻译

托福TPO/Official 54 Passage 3阅读原文Look at the four squares  that indicate where the following sentence could be added to the passage. To answer the question “Could life exist on other planets?” we must first look at the necessary preconditions for life.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.题目答案及解析-新东方托福官方网校手机版

生命的出现需要一系列化学元素来构成细胞的组成部分。

The creation of life requires a set of chemical elements for making the components of cells.

地球上的生命使用了92种天然的化学元素中的25种，尽管其中仅有四种元素（氧、碳、氢和氮）构成了生物体质量的96%。

Life on Earth uses about 25 of the 92 naturally occurring chemical elements, although just 4 of these elements—oxygen, carbon, hydrogen, and nitrogen—make up about 96 percent of the mass of living organisms.

因此，生命的第一要素可能是生物所需的大多数或者所有元素的存在。

Thus, a first requirement for life might be the presence of most or all of the elements used by life.

有趣的是，这个要求几乎可以在任何世界上得到满足。

Interestingly, this requirement can probably be met by almost any world.

科学家们已经确定，宇宙中除了氢和氦（以及微量的锂）之外，所有的化学元素都是由恒星产生的。

Scientists have determined that all chemical elements in the universe besides hydrogen and helium (and a trace amount of lithium) were produced by stars.

这些都是重元素，因为他们的质量比氢和氦更大。

These are known as heavy elements because they are heavier than hydrogen and helium.

尽管与氢和氦相比，这些重元素相当稀少，但它们几乎在所有地方都能找到。

Although all of these heavy elements are quite rare compared to hydrogen and helium, they are found just about everywhere.

恒星持续制造重元素，并通过恒星的死亡将其释放到太空中，因此，随着时间的推移，重元素相对于氢和氦的数量逐渐增加。

Heavy elements are continually being manufactured by stars and released into space by stellardeaths, so their amount compared to hydrogen and helium gradually rises with time.

重元素约占我们太阳系化学成分（按质量计算）的2%，其余98%为氢和氦。

Heavy elements make up about 2 percent of the chemical content (by mass) of our solar system; the other 98 percent is hydrogen and helium.

在一些非常古老的恒星系统中，这些系统在许多重元素产生之前形成，重元素的比例可能低于0.1%。

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.

然而，已研究的每个恒星系统中至少包含生命所需的所有元素的一部分。

Nevertheless, every star system studied has at least some amount of all the elements used by life.

此外，当微行星——在早期太阳系中形成的微小固态物体，可能会累积成行星——在一个形成中的恒星系统内凝结时，它们不可避免地由重元素组成，因为更常见的氢和氦保持气态。

Moreover, when planetesimals—small, solid objects formed in the early solar system that may accumulate to become planets—condense within a forming star system, they are inevitably made from heavy elements because the more common hydrogen and helium remain gaseous.

因此，任何地方的小行星体都应包含生命所需的元素，这意味着由小行星体构建的天体——如行星、月球、小行星和彗星——也包含这些元素。

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.

太阳系形成的特性解释了为什么地球包含生命所需的所有元素，这也是我们预期这些元素存在于整个太阳系、银河系及宇宙中其他世界的原因。

The nature of solar-system formation explains why Earth contains all the elements needed for life, and it is why we expect these elements to be present on other worlds throughout our solar system, galaxy, and universe.

请注意，即使我们考虑与地球生命非常不同的生命形式，这一论点仍然不变。

Note that this argument does not change, even if we allow for life very different from life on Earth.

地球上的生命是以碳为基础，大多数生物学家相信其它星球的生命也可能以碳为基础。

Life on Earth is carbon based, and most biologists believe that life elsewhere is likely to be carbon based as well.

然而，我们也不能完全排除以其它化学物质为基础的生命的可能性，比如硅或氮。

However, we cannot absolutely rule out the possibility of life with another chemical basis, such as silicon or nitrogen.

以其它元素为基础的生命使用的元素（或者是相对的比例）可能与地球上以碳为基础的生命有所不同。

The set of elements (or their relative proportions) used by life based on some other element might be somewhat different from that used by carbon-based life on Earth.

但这些元素仍然是恒星的产物，并且以小行星体的形式存在于任何地方。

But the elements are still products of stars and would still be present in planetesimals everywhere.

无论我们寻找何种类型的生命，我们都可能在宇宙中几乎所有的行星、月球、小行星和彗星上找到所需的元素。

No matter what kinds of life we are looking for, we are likely to find the necessary elements on almost every planet, moon, asteroid, and comet in the universe.

一个更为严格的要求是这些元素以可用作生命现成构建块的分子形式存在，正如早期地球上可能存在的氨基酸有机汤和其他复杂分子。

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.

地球上的有机分子可能来源于三种途径的某种组合：大气中的化学反应、海洋中深海热泉附近的化学反应，以及小行星和彗星携带到地球的分子。

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.

前两种来源分别只能在拥有大气层或海洋的世界上发生。

The first two sources can occur only on worlds with atmospheres or oceans, respectively.

但第三种来源应已将相似的分子带到我们太阳系的几乎所有世界。

But the third source should have brought similar molecules to nearly all worlds in our solar system.

对陨石和彗星的研究表明，有机分子在小行星和彗星中广泛存在。

Studies of meteorites and comets suggest that organic molecules are widespread among both asteroids and comets.

由于在所谓的重度撞击期（约40亿年前），太阳系中的每个天体都反复受到小行星和彗星的撞击，因此每个天体应至少接收了一些有机分子。

Because each body in the solar system was repeatedly struck by asteroids and comets during the period known as the heavy bombardment (about 4 billion years ago), each body should have received at least some organic molecules.

然而，这些分子往往在未受大气保护的表面被太阳辐射破坏。

However, these molecules tend to be destroyed by solar radiation on surfaces unprotected by atmospheres.

此外，尽管这些分子可能在表面下保持完整（如同它们在小行星和彗星上明显存在），但除非有某种液体或气体环境来促使它们移动，否则它们可能无法相互反应。

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.

因此，如果我们将搜索范围限定在有机分子可能参与化学反应的世界上，我们可能会排除任何缺乏大气层和表面或地下液态介质（如水）的世界。

Thus, if we limit our search to worlds on which organic molecules are likely to be involved in chemical reactions, we can probably rule out any world that lacks both an atmosphere and a surface or subsurface liquid medium, such as water.

The word “components” in the passage is closest in meaning to

Why does the author provide the information that "Heavy elements...stellar deaths"?

Paragraph 3 suggests that which of the following may be a difference between very old star systems and newer star systems?

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.

According to paragraph 4, which of the following is true about possible life on other planets?

According to paragraph 5, all of the following are true of the organic molecules on early Earth EXCEPT:

The word “intact” in the passage is closest in meaning to

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?

Look at the four squares  that indicate where the following sentence could be added to the passage. To answer the question “Could life exist on other planets?” we must first look at the necessary preconditions for life.  Where would the sentence best fit? Click on a square  to add the sentence to the passage.

Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

Elements of Life 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, although just 4 of these elements—oxygen, carbon, hydrogen, and nitrogen—make up about 96 percent of the mass of 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 have determined that all chemical elements in the universe besides hydrogen and helium (and a trace amount of lithium) were produced by stars. These are known as heavy elements because they are heavier than hydrogen and helium. Although all of these heavy elements are quite rare compared to hydrogen and helium, they are found just about everywhere. Heavy elements are continually being manufactured by stars and released into space by stellardeaths, so their amount compared to hydrogen and helium gradually rises with time. Heavy elements make up about 2 percent of the chemical content (by mass) of our solar system; the other 98 percent is hydrogen and helium. 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 at least some amount of all the elements used by life. Moreover, when planetesimals—small, solid objects formed in the early solar system that may accumulate to become planets—condense within a forming star system, they are inevitably made from heavy elements because the more common hydrogen and helium remain gaseous. 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. The nature of solar-system formation explains why Earth contains all the elements needed for life, and it is why we expect these elements to be present on other worlds throughout our solar system, galaxy, and universe. Note that this argument does not change, even if we allow for life very different from life on Earth. Life on Earth is carbon based, and most biologists believe that life elsewhere is likely to be carbon based as well. However, we cannot absolutely rule out the possibility of life with another chemical basis, such as silicon or nitrogen. The set of elements (or their relative proportions) used by life based on some other element might be somewhat different 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 every planet, moon, asteroid, and comet in the universe. 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. 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. The first two sources can occur only on worlds with atmospheres or oceans, respectively. But the third source should have brought similar molecules to nearly all worlds in our solar system. Studies of meteorites and comets suggest that organic molecules are widespread among both asteroids and comets. Because each body in the solar system was repeatedly struck by asteroids and comets during the period known as the heavy bombardment (about 4 billion years ago), 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. Thus, if we limit our search to worlds on which organic molecules are likely to be involved in chemical reactions, we can probably rule out any world that lacks both an atmosphere and a surface or subsurface liquid medium, such as water.