2015年7月5日托福阅读真题+题目+答案+译文：Elements of Life

2015年7月5日托福阅读真题+题目+答案：Elements of Life

1. 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 elementsoxygen, carbon, hydrogen, and nitrogenmake 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.

生命的形成需要一系列构成细胞成分的化学元素，自然界中存在着92种化学元素，地球上的生物大约使用了其中的25种。虽然这些元素中，仅氧、碳、氢和氮这四种元素就约占这些生物96%的质量。因此，生命形成所需的首要条件可能就是具备大部分或者全部构成生命的化学元素。

2. 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.

3. 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. 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 planetesimalssmall, solid objects formed in the early solar system that may accumulate to become planetscondense 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 planetesimalsplanets, moons, asteroids, and cometsalso 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.

有趣的是，在几乎任何一个星球上，这种要求都很可能得到满足。科学家们已经确定，除了氢和氦(以及微量的锂)以外，恒星还能产生宇宙中所含的其他化学元素。 这些被称为重元素,因为它们比氢和氦重。虽然与氢和氦相比，这些重元素全部都相当稀少，但是它们几乎无处不在。恒星不断地产生着重元素，在恒星灭亡后，这些元素被释放到太空中，因此它们的数量与氢和氦相比，是随着时间的推移逐渐增长的。重元素构成了我们太阳系约2%的化学成分(在质量上);剩下的98%则由氢和氦构成。在一些非常老的恒星星系，它们在很多重元素产生之前就已经形成，其中的重元素含量可能不到0.1个百分点。虽然如此，研究表明，每一个恒星星系都至少含有一定数量的、生命所需的各种元素。此外，当星子中在太阳系早期形成的小固体物质逐渐积累，可能成为某个正在形成中的恒星星系内部的行星时，它们将不可避免地由重元素构成，因为更常见的氢和氦还是气体形态。因此，星子应该都包含构成生命所需的元素，这也意味着星子行星、卫星、小行星和彗星上形成的物质也含有这些元素。太阳系形成的原理可以解释为什么地球含有所有生命形成所需的全部元素，同时也是我们认为其他的星球具备这些元素的依据，这些星球不仅存在于我们的太阳系，还遍布在银河和宇宙中。

。。。。。此处省略余下原文！

托福阅读真题题目：

1..The word components in the passage is closest in meaning to

A. parts

B. bodies

C. combinations

D. characteristics

2..According to paragraphs 1 and 2, living cells contain which of the following

A. All chemical elements in the universe except lithium

B. About 25 different elements

C. About 96 percent of all known elements

D. Ninety-two naturally occurring elements

3..Why does the author provide the information that "Heavy elements are continually being manufactured by stars and released into space by stellar deaths"

A. To explain how it is that the elements required for life can be found everywhere

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

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

D. To explain why heavy elements have greater mass than hydrogen and helium

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

A. Older star systems are likely to have fewer planets, moons, asteroids, and comets than newer star systems.

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

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

D. The process of solar-system formation may have been fundamentally different in older star systems than in newer star systems.

。。。。。此处省略余下题目和答案！

2015年7月5日托福阅读真题+题目+答案：Elements of Life，完整版下载，10元有偿！