为适应井下的测量条件，在选用各种经纬仪时应力求满足（）等要求。
A.仪器结构紧凑、轻便耐用、密封性好
B.具有防爆照明系统，便于井下读数及十字丝照准目标
C.具有镜上中心，以便于仪器点下对中
D.为了便于观测近目标或测设腰线，仪器最短视距应小于1-2米左右
E.为了便于井下安置仪器，又不影响运输，经纬仪应具有可伸缩性的三角架或托盘
参考答案：A, B, C, D, E
| Questions 91-95 are based on the following passage. It is amazing how many people still say, "I never dream", for it is now decades since it was established that everyone has over a thousand dreams a year, however few of these nocturnal productions are remembered on waking. Even the most confined "non-dreamers" will remember dreams if woken up systematically during the Rapid Eye Movement (REM) periods. These are periods of light sleep during which the eyeballs move rapidly back and forth under the closed lids and the brain becomes highly activated, which happens three or four times every night of normal sleep. It is a very interesting question why some people remember dreams regularly—perhaps several a night on occasion—while others remember hardly any at all under normal conditions. In considering this, it is important to bear in mind that the dream tends to be an elusive phenomenon for all of us. We normally never recall a dream unless we awaken directly from it, and even then it has a tendency to fade quickly into oblivion. Given this general elusiveness of dreams, the basic factor that seems to determine whether a person remembers them or not is the same as that which determines all other memory, namely degree of interest. Dream researchers have made a broad classification of people into "recallers" —those who remember at least one dream a month—and "non-recallers", who remember fewer than this. Tests have shown that cool, analytical people with a very rational approach to their feelings tend to recall fewer dreams than those whose attitude to life is open and flexible. Engineers generally recall fewer dreams than artists. It is not surprising to discover that in western society, women normally recall more dreams than men, since women are traditionally allowed an instinctive, feeling approach to life. In modern urban-industrial culture, feeling and dreams tend to be treated as frivolities which must be firmly subordinated to the realities of life. We pay lip-service to the inner life of imagination as it expresses itself in the arts, but in practice relegate music, poetry, drama and painting to the level of spare-time activities, valued mainly for the extent to which they refresh us for a return to work. We discourage our children from paying much attention to anything that might detract from the serious business of studying for exams or making a living in the "real" world of industry and commerce. |
Many people are unaware that they dream because ______.
A．their dreams fade very quickly
B．they do not recall their dreams
C．they sleep too heavily
D．they wake up frequently