新发现破解未解之谜：火星上是否有生命

Scientists have found a kind of poisonous chemical on Mars. It would kill any living thing. The scientists say the discovery of the chemical means the chance of finding life on Mars is very low. Mars has no ozone layer(臭氧层). This means there are high levels of ultra-violet (紫外线) radiation. This mixes with the chemicals and makes it impossible for anything to grow on Mars.
The scientists said that just the chemical was enough to kill living things. When they mix with ultra-violet rays, the mix kills living things 11 times faster. The scientists said, "The surface of Mars is highly harmful to cells, caused by the poisonous chemical and ultra-violet radiation." They say their research is evidence that the land on Mars is deadly to any kind of living things. They say the chemical and ultra-violet rays make much of the surface and near-surface regions uninhabitable.

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1.The poisonous chemical on Mars would kill ___ .

A plants

B animals

C human beings

D any living thing

解析：选D。细节理解题。根据第一段第一、二句Scientists have found a kind of poisonous chemical on Mars. It would kill any living thing. 可知科学家们在火星上发现了一种有毒的化学物质，它会杀死任何生物，故选D。

2.From Paragraph 1, what does “Mars has no ozone layer” mean?

A It means there is no night and stars.

B It means there is no sunshine and no day.

C It means there are high levels of ultra-violet radiation on Mars.

D It means there is no weekend and no holiday.

解析：选C。细节理解题。根据第一段第四、五句Mars has no ozone layer(臭氧层). This means there are high levels of ultra-violet (紫外线) radiation.可知火星没有臭氧层。这意味着有很强的紫外线辐射，故选C。

3.What does “mix”refer to?

A The chemical.

B Ultra-violet rays.

C Living things.

D Both A and B.

解析：选D。细节理解题。根据第二段第一、二句The scientists said that just the chemicals were enough to kill living things. When they mix with ultra-violet rays, the mix kills living things 11 times faster.可知科学家说，这些化学物质足以杀死生物。当它们与紫外线混合时，混合物杀死生物的速度是原来的11倍，故选D。

4.What causes the surface of Mars highly harmful to cells?

A Pollution.

B The poisonous chemical and ultra-violet radiation.

C Overpopulation.

D The polluted sky, rivers and earth.

解析：选B。细节理解题。根据第二段第三句The scientists said， "The surface of Mars is highly harmful to cells, caused by the poisonous chemical and ultra-violet radiation."可知科学家们说：“火星表面对细胞十分有害，是由化学物质和紫外线辐射引起的。”故选B。

5.What’s the meaning of “uninhabitable”in Chinese?

A 不适合居住的

B 感兴趣的

C 适合居住的

D 不舒服的

解析：选A。词义猜测题。根据上文可知，由于化学物质和紫外线，使得火星大部分的表面和近表面区域不适合居住。故选A。