Many scientists today are convinced that life exists elsewhere in the universe-life probably much like that on our own planet. They reason in the following way. As far as astronomers can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe. Therefore, it is reasonable to guess that other stars, with their own planets, were born in the same way as our own solar system. What we know of life on earth suggests that life will arise wherever the proper conditions exist. Life requires the right amount and kind of atmosphere. This eliminates all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere; a larger one would hold too much of it. Life also requires a steady supply of heat and light. This eliminates double stars, or stars that flare up suddenly. Only single stars that are steady sources of heat and light like our sun would qualify. Finally, life could evolve only if the planet is just the right distance from its sun. With a weaker sun than our own, the planet would have to be closer to it. With a stronger sun, it would have to be farther away. If we suppose that every star in the universe has a family of planets, then how many planets might support life? First, eliminate those stars that are not like our sun. Next eliminate most of their planets; they are either too far from or too close to their suns. Then eliminate all those planets which are not the same size and weight as the earth. Finally, remember that the proper conditions do not necessarily mean that life actually does exist on a planet. It may not have begun yet, or it may have already died out. This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist.
单选题
Astronomers believe that matter in different parts of the universe ______.
【正确答案】
C
【答案解析】[解析] 推断题。根据第二段前两句：As far as astronomers can determine, the entire universe is built of the same matter. They have no reason to doubt that matter obeys the same laws in every part of the universe．天文学家现在可以确定整个宇宙是由同种物质组成的。他们没有理由怀疑宇宙的每一部分中的物质都遵守同样的法则。可以推断C为正确选项。
单选题
The existence of life depends on all of the following factors EXCEPF ______.
【正确答案】
B
【答案解析】[解析] 推断题。A选项和第三段句Life requires the right amount and kind of atmosphere(生命需要适量的和适合种类的大气层)一致，C选项和第四段主题句Life also requires a steady supply of heat and light(生命还需要稳定的光和热的供应)一致，D和第五段主题句Finally, life could evolve only if the planet is just the right distance from its sun．(最后，只有行星和它的太阳之间的距离恰好时，生命才可以衍生)一致，因此选B。
单选题
Which of the following statements is INCORRECT?
【正确答案】
C
【答案解析】[解析] 细节题。A选项和第三段中的This eliminates all those planets in the universe that are not about the same size and weight as the earth. A smaller planet would lose its atmosphere; a larger one would hold too much of it．相一致，即那些星球必须和地球一样大一样重才可以有生命。根据第二段：what we know of life on earth suggests, that life will arise wherever the proper conditions exist．我们地球上的生命法则告诉我们只要有适合条件，那里都可以出现生命 以及下面所列举的三个生命存在的条件，可以推断出生命的存在必须有一定的条件，B选项和这个意思一致。D选项是第五段主题句Finally, life could evolve only if the planet is just the right distance front its sun一致。根据第四段Life also requires a steady supply of heat and light. This eliminates double stars, or stars that flare up suddenly. Only single stars that are steady sources of heat and light like our sun would qualify．生命还需要稳定的光和热的供应。这条就排除了双子星或突然形成的星球。只有如太阳一样的单体星球才能成为稳定的热源和光源，以判断双子星无法提供稳定的热源和光源，因此C是错误。
单选题
At the end of the passage the author suggests that ______.
【正确答案】
D
【答案解析】[解析] 推断题。最后一段中：This process of elimination seems to leave very few planets on which earthlike life might be found. However, even if life could exist on only one planet in a million, there are so many billions of planets that this would still leave a vast number on which life could exist．虽然第一句似乎是在说earthlike life could only exist on a few planets．即B选项的内容，但是马上用However一转折，用来强调后面的内容，即：即使一百万个行星中有一个行星上存在生命，但宇宙中有无数的数以十亿计的行星，这样的话，仍有相当大数量的行星上可能存在生命。这个和D选项内容一致。