Being alone in outer space can be fright

问题：

Being alone in outer space can be frightening. That is one reason why astronauts on solo (单独的) space flights were given plenty of work to keep them  21 . They were also constant communication with people on the earth.  22 , being with people from whom you cannot get away might be even harder than being alone. This is what happens on long submarine (潜水艇) voyages. It will also happen on  23  space flights in the future. Will there be special problem of adjustment under such conditions?

Scientists have studied the reactions of men to one another during long submarine voyages. They have found that the longer the voyage lasts, the more serious the problem of 24  is. When men are  25  together for a long period, they begin to feel uneasy. Everyone has little habits of speaking and behaving that are ordinarily acceptable. In the limited space over a long period of time, however, these little habits may become very  26 .

Apparently, although no one wants to be  27  all the time, everyone needs some degree of privacy. When people are enclosed together, they are in what is called a stress situation. That means that they are under an unusual amount of  28  or stress.

People who are well-adjusted are able to  29 stress situations better than others. That is one reason why so much care is taken in  30  our astronauts. These men undergo a long period of testing and training. One of the things tested is their behavior under stress.

21. A. tired                    B. asleep                 C. conscious            D. busy

22. A. So far                  B. After all              C. However             D. Therefore

23. A. long                    B. fast                     C. dangerous            D. direct

24. A. fuel                     B. entertainment       C. adjustment           D. health

25. A. shut up                B. held up               C. brought up          D. picked up

26. A. pleasing               B. annoying             C. common              D. valuable

27. A. noisy                   B. alone                  C. personal              D. sociable

28. A. emphasis              B. conflict               C. power                 D. pressure

29. A. handle                 B. create                  C. affect                  D. investigate

30. A. becoming             B. choosing             C. ordering              D. promoting