Medical experts say most Americans do not get _____51 sleep. They say more Americans need to rest for a short period in the middle of the day. They are advising people to sleep lightly before_____ 52 with other activities.

　　One study earlier this year found that persons who sleep for a few minutes during the day were less _____53 to die of heart disease. The study followed more than 2,300 Greek adults _____54 about six years. Adults who rested for half an hour _____55 three times a week had a 37 present lower risk of dying from heart disease than those who did not nap.

　　Study organizers said the strongest evidence was in working men. They said naps might improve_____ 56 by mitigating tension caused by work.

　　Some European and Latin American businesses have supported the _____57 of napping for many years. They urge people to _____58 work, go home and have a nap before returning. In the United States, some companies let workers rest briefly in their offices. They believe this reduces _____59 and accidents, and _____60 increases the amount of work a person can do.

　　Sleep experts say it is likely that people make more mistakes at work than at other times. They say people should not carry out important duties when they feel _____61 And they say the best thing to do is to take a nap. About twenty minutes of rest is _____62 you need. Experts say this provides extra energy and can increase your effectiveness _____63 the end of the day. But experts warn that a nap _____64 last no more than twenty to thirty minutes. A longer nap will put the body into deep sleep and waking up will be _____65 .

　　練習(xí)：

　　51. A sweet B sound C bad D enough

　　52. A checking B sharing C continuing D meeting

　　53. A lovely B likely C fondly D finely

　　54. A for B at C in D with

　　55. A at least B at most C at last D at first

　　56. A ability B health C thinking D life

　　57. A experiment B reform C idea D way

　　58. A repeat B improve C change D leave

　　59. A work B mistakes C energy D time

　　60. A never B seldom C too D also

　　61. A ready B good C sleepy D awake

　　62. A all B few C any D nothing

　　63. A unless B while C until D during

　　64. A would B may C might D should

　　65. A helpful B difficult C easy D happy

　　答案：DCBAA BCDBD CACDB