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【B1】_____ a

Space is a dangerous place, not only because of meteors(流星)but also because of rays from the sun and other stars. The【B1】_____ a

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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【B1】_____ again acts as our protective blanket on earth Light gets through, and this is【B2】_____ for plants to make the food which we eat. Heat, too, makes our environment【B3】_____. Various kinds of rays come through the air from outer space, but enormous quantities of radiation from the sun are【B4】_____ off. As soon as men leave the atmosphere they are exposed to this【B5】_____ and their spacesuits or the walls of their spacecraft, if they are inside, do【B6】_____ a lot of radiation damage.
    Radiation is the greatest known danger to【B7】_____ 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【B8】_____ difficult to be sure about radiation damage—【B9】______, and this will not be discovered until the birth of deformed children or even grandchildren. Missions of the Apollo flights have had to cross belts of high amounts of rems.【B10】______, 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,【B11】______
【B3】
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