We all know that the normal human daily cycle of activity is of .some 7-8 hours’ sleep alternating with some 16-17 hours’ wakefu

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问题     We all know that the normal human daily cycle of activity is of .some 7-8 hours’ sleep alternating with some 16-17 hours’ wakefulness and that, broadly speaking, the sleep normally coincides with the hours of darkness. Our present concern is with how easily and to what extent this cycle can be modified.
    The question is no mere academic one. The ease, for example, with which people can change from working in the day to working at night is a question of growing importance in industry where automation calls for round the-clock working of machines. It normally takes from five days to one week for a person to adapt to a reversed routine of sleep and wakefulness, sleeping during the day and working at night. Unfortunately, it is often the case in industry that shifts are changed every week, a person may work from 12 midnight to 8 a. m one week, 8 a.m. to 4 p.m. the next, and 4p. m to 12 midnight the third and so on. This means that no sooner has he got used to one routine than he has to change to another, so that much of his time is spent neither working nor sleeping very efficiently.
     The only real solution appears to be handed over the night shift to a number of permanent night workers. An interesting study of the domestic life and health of night-shift workers was carried out by Brown in 1957. She found a high incidence of disturbed sleep and other disorders among those on alternating day and night shifts, but no abnormal occurrence of these phenomena among those on permanent night work.
     The latter system then appears to be the best long-term policy, but meanwhile something may be done to relieve the strains of alternate day and night work by selecting those people who can adapt most quickly to the changes of routine. One way of knowing when a person has adapted is by measuring his body temperature. People engaged in normal daytime work will have a high temperature during the hours of wakefulness and low one at night; when they change to night work the pattern will only gradually go back to match the new routine and the speed with which it does so parallels, broadly speaking, the adaptation of the body as a whole, particularly in terms of performance. Therefore, by taking body temperature at intervals of two hours throughout the period of wakefulness it can be seen how quickly a person can adapt to a reversed routine, and this could be used as basis for selection. So far, however, such a form of selection does not seem to have been applied in practice.
The main problem of the round-the-clock working system lies in ______.

选项 A、the inconveniences brought about to file workers by the introduction of automation
B、the disturbance of daily life cycle of workers who have to change shifts too frequently
C、the fact that people working at night are often less effective
D、the fact that it is difficult to find a number of good night workers

答案B

解析 推理题。本题要求抓住第二段的中心大意,根据第二段最后一句话,“工人刚刚习惯了某一班次的时间安排,却又要倒班了。这样他大部分时间工作和睡眠效率都不高”。所以关键在于工人的日常生活周期规律被打乱了。选项A文章没有提及。选项C不符合文章原意,文章是说工人在适应新的工作班次之前效率不高,并不只是夜间工作效率不高。选项D文章没有提及。
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