单选题 {{B}}第三篇{{/B}}

Sleep Deficit(不足)

Judging from recent surveys, most experts in sleep behavior agree that 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. Even people who think they are sleeping enough would probably be better off with more rest.
The beginning of our sleep-deficit crisis can be traced to the invention of the light bulb a century ago. From diary entries and other personal accounts from the 18th 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 8 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 7.5,8 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 program. "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 consequences 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 re call a page read to them only minutes earlier. "We've found that if you're in sleep deficit, perform ance suffers," says Dr. David. "Shot-term memory is weakened, as are abilities to make decision and to concentrate.

单选题 People in the 18th and 19th centuries used to sleep about 9.5 hours a night because they had ______.

【正确答案】 B

【答案解析】[解析] 细节题。第二段的第二、三句说From dairy 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.”可知，以前夜晚一片漆黑，人们没有事做，因而那时的人们养成了最佳睡眠习惯。本段首提到了睡眠不足是因为电灯泡的发明，可推知18、19世纪的人生因为没有照明，导致没有事情可做，因而养成了早睡觉的习惯。因此，B符合文意。A“没有精力和野心”和C“有最好的睡眠习惯”使用文中的只言片语进行干扰，不正确；D“第二天又很多事情要做”文中没有提及。

单选题 According to Dr. David, Americans ______.

【正确答案】 B

【答案解析】[解析] 推断题。在第二段后半部分中大卫博士提到其实在睡眠上人们在自欺欺人，只是他们没有意识到而已，并且人们认为每天睡6.5小时他们完全可以应付。事实上。要确保精力充沛，他们需要7.5至8小时，甚至更长时间的睡眠。在第3段中，大卫博士指出，每当面对工作、家人、朋友和社会的巨大压力时，很多人认为睡眠是最不重要的，是最可以有弹性的。由此不难得出结论，美国人不在乎睡眠不足的后果或对此视而不见，因此B符合文意。

单选题 Many Americans believe that ______.

【正确答案】 A

【答案解析】[解析] 推断题。根据第三段内容可知，美国人往往减少睡眠时间的方式来处理生活中的事情，因为睡眠是最不重要的(the least expensive item)。因此，A符合文意。B“需要更多的睡眠去应对生活压力”与文意正好相反；C“一天任何时候都可以用来睡觉”和D“充足的睡眠可以提升精力和野心”文中没有提及。

单选题 The word "subjects" (line 1, Para.4 ) refers to ______.

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

【正确答案】 D

【答案解析】[解析] 推断题。由最后一段研究结果We've found that if you're in sleep deficit,performance suffers…Short-term memory is weakened，as are abilities to make decision and to concentrate.可知，睡眠关系到人的精力和表现，因此，D符合文意。虽说文章在最后一段提到了睡眠不足时，瞬时记忆力会下降，但并没没有说睡多了可以提高记忆力，因此A“大幅度提高记忆力”不正确；B“被认为精力充沛”是对原文的曲解；C“维持某人的日常时间安排”文中并未提及。