Space is a dangerous place, not only because of meteors(流星) but also becaus

游客2024-10-21 10

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. [br] The best title for this passage would be ______.

选项 A、The Atmosphere and Our Environment
B、Research on Radiation
C、Effects of Space Radiation
D、Importance of Protection Against Radiation

答案 C

解析大意判断题。文章第一段指出，太空是一个危险的地方主要是因为太空辐射。离开大气层的宇航员虽有宇航服及宇航船的保护，但也免不了接受辐射。文章第二段指出辐射危害在短期内难以觉察，药物可以减轻辐射危害，但真正有效的药物迄今还未被发现。由此可以看出文章谈及的主要是太空辐射的后果方面的事，所以选项C为正确答案。

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