社会主义和资本主义的本质区别是（） A.生产力的性质和发展水平不同 B.社会基本矛盾

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

水沸腾时，大量水分子吸热变成水蒸气进入空气中，且水从火中得到的热能全部用来让水分子吸热变成水蒸气进入空气中，直到水烧干。正确的推论是( )。

A．一个大气压时，100纯水开始沸腾

B．水分子吸热变成水蒸气

C．水沸腾时温度保持恒定

D．水沸腾时温度继续升高直至烧干

根据《保险营销员管理规定》，保险营销员代为办理保险业务，与保险公司签订委托协议时受到的限制是（）。

A.不得同时与两家或者两家以上保险公司签订委托协议

B.可以与两家或者两家以上保险公司签订委托协议

C.必须与两家或者两家以上保险公司签订委托协议

D.一般与两家或者两家以上保险公司签订委托协议

局部通风机在恢复通风前，必须证实停风区中二氧化碳浓度不超过1％。（）

玉米大豆通用的除草剂（）。

A.乙草胺

B.施田补

C.甲草胺

D.莠去津