(单选题)
The author discusses environments (Line2) in Para. 2 in order to ______.
A.propose that cosmic radiation would have little effect on the lunar colonists
B.indicate that long-term exposure to radiation on atmosphere-less Mars could prove fatal.
C.express the notion that Mars poses less life-threatening hazards than the moon.
D.propose that potential sources of water on Mars make it a better long-term option.
参考答案：C
参考解析：
推理判断题。该题可定位到第二段最后一句“Although Mars’ atmosphere is significantly thinner than Earths’, at least it has one and would create some sort of protective barrier for humans.”尽管火星的大气层比地球的要稀薄地多，但至少火星有大气，这会给人类创造某种保护屏障。而月球是没有大气的。故选C。
知识点：
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