Passage Three

　　Questions 31 to 35 are based on the following passage:

　　Judging from recent surveys, most experts in sleep behavior agree that there is virtually an

　　epidemic(流行病) of sleepiness in the nation. "I can't think of a single study that hasn't

　　found Americans getting less sleep than they ought to," says Dr. David. Even people who think

　　they are sleeping enough would probably be better off with more rest.

　　The beginning of our sleep - deficit (睡眠不足) crisis can be traced to the invention of the

　　light bulb a century ago. From diary entries and other personal accounts from the 18th and 19th

　　centuries sleep scientists have reached the conclusion that the average person used to sleep

　　about 9.5 hours a night. "The best sleep habits once were forced on us, when we had nothing to

　　do in the evening down on the farm, and it was dark. "By the 1950s and 1960s, that sleep

　　schedule had been reduced dramatically, to between 7.5 and eight hours, and most people had

　　to wake to an alarm clock. "People cheat on their sleep, and they don't even realize they' re doing it, "says Dr. David. "They think they' re okay because they can get by on 6.5 hours, when

　　they really need 7.5, eight or even more to feel ideally vigorous."

　　Perhaps the most merciless robber of sleep, researchers say, is the complexity of the day.

　　Whenever pressures from work, family, friends and community mount, many people consider

　　sleep the least expensive item on his programme. "In our society, you' re considered dynamic if

　　you say you only need 5.5 hours' sleep. If you've got to get 8.5 hours, people think you lack

　　drive and ambition."

　　To determine the consequnces of sleep deficit, researchers have put subjects through a set

　　of psychological and performance tests requiring them, for instance, to add columns of numbers

　　or recall a passage read to them only minutes earlier. "We' ye found that if you' re in sleep

　　deficit, performance suffers, "says Dr. David. "Short - term memory is weakened, as are abilities

　　to make decisions and to concentrate."

　　31. People in the 18th and 19th centuries used to sleep about 9.5 hours a night because they

　　had

　　A) no drive and ambition                B) no electric lighting

　　C) the best sleep habits                 D) nothing to do in the evening

　　32. According to Dr. David, Americans

　　A) are ideally vigorous even under the pressure of life

　　B) often neglect the consequences of sleep deficit

　　C) do not know how to relax themselves properly

　　D) can get by on 6.5 hours of sleep

　　33. Many Americans believe that __

　　A) sleep is the first thing that can be sacrificed when one is busy

　　B) they need more sleep to cope with the complexities of everyday life

　　C) to sleep is something one can do at any time of the day

　　D) enough sleep promotes people's drive and ambition

　　34. The word "subjects" (Line 1, Para.4)refers to

　　A) the performance tests used in the study of sleep deficit

　　B) special branches of knowledge that are being studied

　　C) people whose behavior or reactions are being studied

　　D) the psychological consequences of sleep deficit

　　35. It can be concluded from the passage that one should sleep as many hours as is necessary to

　　A) improve one's memory dramatically

　　B) by considered dynamic by other people

　　C) maintain one's daily schedule

　　D) feel energetic and perform adequately