2. 外语
  3. Space is a dangerous place, not only because of meteors (流星) but also because of rays from the sun and other stars. The atmosphe

Space is a dangerous place, not only because of meteors (流星) but also because of rays from the sun and other stars. The atmosphe

admin2012-07-17  51
问题     Space is a dangerous place, not only because of meteors (流星) but also because of rays from the sun and other stars. The atmosphere again acts as our protective blanket on earth. Light gets through, and this is essential for plants to make the food which we eat. Heat, too, makes our environment endurable. Various kinds of rays come through the air from outer space, but enormous quantities of radiation from the sun are screened off. As soon as men leave the atmosphere they are exposed to this radiation but their spacesuits or the walls of their spacecraft, if they are inside, do prevent a lot of radiation damage.
    Radiation is the greatest known danger to explorers in space. The unit of radiation is called "rem". Scientists have reason to think that a man can put up with far more radiation than 0. 1 rem without being damaged; the figure of 60 rems has been agreed on. The trouble is that it is extremely difficult to be sure about radiation damage—a person may feel perfectly well, but the cells of his or her sex organs may be damaged, and this will not be discovered until the birth of deformed (畸形的) children or even grandchildren. Missions of the Apollo flights have had to cross belts of high radiation and, during the outward and return journeys, the Apollo crew accumulated a large amount of rems. So far, no dangerous amounts of radiation have been reported, but the Apollo missions have been quite short. We simply do not know yet how men are going to get on when they spend weeks and months outside the protection of the atmosphere, working in a space laboratory. Drugs might help to decrease the damage done by radiation, but no really effective ones have been found so far.
According to the first paragraph, the atmosphere is essential to man in that______.
选项 A、it protects him against the harmful rays from space
B、it provides sufficient light for plant growth
C、it supplies the heat necessary for human survival
D、it screens off the falling meteors
答案A
解析 本题问按照文章第一段的内容，大气层对人类非常重要的原因是什么。仔细阅读第一段内容可知，太空是个危险的地方，不仅流星四布，且有太阳和其他星体的辐射。大气层对地球起了一种保护作用。一旦人们离开大气层，就会直接暴露在太阳辐射之中。我们不难看出本题的正确答案应是A“大气层可以保护人类免受太阳辐射的伤害”。
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