Part Ⅳ CLOZE ［15 MIN.］
Decide which of the choices given below would best complete the passage if inserted in the corresponding blanks. Mark the best choice for each blank on your answer sheet.?

The normal human daily cycle of activity is of some 7-8 hours' sleep alternation with some 16-17 hours' wakefulness and that the sleep normally coincides(26) ____ the hours of darkness. Our present concern is with how easily and to what extent this(27)____ can be modified.?
The question is no mere academic one. The ease with which people can change from working in the day to working at night is a(28)____ of growing importance in industry where automation(29)____ round-the-clock working of machines. It normally(30)____ from five days to one week for a person to adapt to a?(31)____? routine of sleep and wakefulness, sleeping during the day and working at night. ?(32)____,? it is often the case in industry that shifts are changed every week. This means that no sooner has he got used to one routine(33)____ he has to change to another, (34)____ much of his time is spent neither working nor sleeping very(35) ____.?
One answer would seem to be(36)____ periods on each shift, a month, or even three months. (37)____, recent research has shown that people on such systems will revert to go back to their(38)____ habits of sleep and wakefulness during the week-end and that this is quite enough to destroy any(39)____ to night work built up during the week. The only real solution appears to be to hand over the night shift to those permanent night workers whose(40)____ may persist through all week-ends and holidays.

26.A.in B.with C.of D.over??
27.A.cycle B.period C.circle D.round???
28.A.problem B.difficulty C.trouble D.matter??
29.A.asks B.invites C.calls for D.reacts to?
30.A.takes B.spends C.demands D.asks?

31.A.former B.returned C.reversed D.regular??
32.A.Therefore B.Unfortunately?C.In a word D.In comparison??
33.A.as B.when C.then D.than?
34.A.though B.so that C.while D.as?
35.A.efficiently B.good C.easily D.happily?

36.A.shorter B.better C.longer D.nicer??
37.A.So B.In short C.Similarly D.However??
38.A.new B.normal C.temporary D.favourite??
39.A.change B.return C.adaptation D.tendency???
40.A.wakefulness B.sleep C.preference D.habit