Passage 5 Judging from recent surveys, most experts in sleep behavior. agree that there is virtually an epidemic 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. The beginning of our sleep deficit crisis can be _1_ to the invention of the light bulb a century ago. From diary entries and other personal _2_ 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. By the 1950s and 1960s, that sleep schedule had been reduced _3_ to between 7.5 and 8 hours, and most people had to wake to an alarm clock. “People cheat on their sleep, and they don’t even _4_ 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 7.5，8 or even more to feel ideally _5_.” Perhaps the most merciless robber of sleep, researchers say, is the _6_ of the day. Whenever pressures from work, family, friends and community mount, many people consider sleep the least _7_ item on the agenda. “In our society, you’re considered dynamic if you say you only need 5.5 hours’ sleep. If you say you’ve got to get 8.5 hours, people think you lack _8_ and ambition.” To assess the _9_ of sleep deficit, researchers have put subjects through a set of psychological and performance tests requiring them. “We’ve found that if you’re sleep-deprived, performance _10_,” says Dr. David. “Short-term memory is impaired, as are abilities to make decisions and to concentrate.” A) consequences B) complexity C) ingenious D) dramatically E) suffers F) tracked G) realize H) expensive I) slightly J) traced K) detaches L) vigorous M) inspiration N) accounts O) drive 第1空答案是：