Being alone in outer space can be frightening. That is one reason why astronauts on solo

Being alone in outer space can be frightening. That is one reason why astronauts on solo（单独的） space flight were given plenty of work to keep them  21   . They were also in 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 problems 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.

21-25  DCACA        26-30 BBDAB