阅读理解。
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 (不可缺少的) 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 (用屏幕隔开). As soon as men leave the
atmosphere, they areexposed to this radiation but their spacesuit 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 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 (积累) 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 don't know yet how men are going to get on when they spent 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.
1. According to the first paragraph, the atmosphere is essential to man in that ________.
A. it protects him against the harmful rays from space
B. it provides sufficient (充分的) light for plant growth
C. it supplies the heat necessary for human survival
D. it screens off the falling meteors
2. The harm radiation had done to the Apollo crew members ________.
A. is insignificant (不重要的)
B. seems overestimated
C. is enormous
D. remains unknown
3. It can be inferred from the passage that _________.
A. the Apollo mission was very successful
B. protection from space radiation is no easy job
C. astronauts will have deformed children or grandchildren
D. radiation is not a threat to well-protected space explorers
4. The best title for this passage would be ______.
A. The atmosphere and Our Environment
B. Research on Radiation
C. Effects of Space Radiation
D. Importance of Protection Against Radiation
