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

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

admin2012-09-19  48
问题     Space is a dangerous place, not only because of meteors (陨星) but also because of rays from the sun and other stars. The atmosphere again acts as our protective blanket on the 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 space suits 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 (雷姆)". 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 rem 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 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 rem. 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 not really effective ones have been found so far.
We know from the passage that______.
选项 A、exposure to even tiny amounts of radiation is fatal
B、the effect of exposure to radiation is slow in coming
C、radiation is avoidable in space exploration
D、astronauts in space suits needn’t worry about radiation damage
答案B
解析 根据第二段“…a person may feel perfectly，and this will not be discovered until the birth of deformed children or even grandchildren”可知B项正确。
转载请注明原文地址:https://www.kaotiyun.com/show/Vg57777K
0

大学英语四级

相关试题推荐
随机试题
最新回复(0)