No one knows why we sleep, but it’s certain that we need to. People who are prevented from sleeping begin to suffer obvious effects after a few days—they think less clearly, and they fall asleep during the working hours.
There are no rules about sleep. Generally speaking, grown-ups sleep about 7 and a half hours each night and probably more than 60 percent get between seven and eight hours. But perhaps eight percent are quite happy with 5 hours or less, and four percent or so find that they want ten hours or more. If you feel all right, you’re probably getting enough sleep. The important thing is not to worry how much other people get—their needs may be different. Exercise doesn’t seem to increase the need for sleep—office workers, for example, sleep for about as long as people doing physically active work.
Children sleep more than grown-ups—perhaps 14 to 18 hours soon after birth, going down to grown-up levels by early teenage (青少年). Sleep patterns also tend (傾向) to be different in the old people, who may sleep less at night than they did when younger, find sleep getting more broken, and often make it a rule to sleep during the daytime.
1. Some people can’t think clearly because _______.
A. they have bad memory B. they feel sleepy during the working hours
C. they don’t have enough sleep D. they are certain to be kept from going to bed
2. Whether you have got enough sleep is judged (判斷) by _______.
A. how many hours you have slept B. how many hours you need to sleep
C. if you do exercise and physical work D. if you feel fresh energetic
3. According to the passage, a boy of 14 years old sleeps _____.
A.as long hours as a grown-up B. much longer hours than a grown-up
C. for 14 hours each night D. for less than 8 hours each night
4. Which of the following is True?
A. All grown-ups much have at least eight-hour sleep.
B. Most of grown-ups sleep for seven or eight hours.
C. Quite a few people need only 5 hours or less for them to sleep.
D. No grown-ups sleep more than ten hours.
【答案與解析】睡覺要占去人一生三分之一左右的時間。人為什么要睡覺？這個問題一直使人們，包括科學(xué)家在內(nèi)，都困惑不解。本文向讀者介紹了不同年齡層次的人們，睡眠的需求也不盡相同。
1.C.A、B兩個答案是睡眠的結(jié)果而不是導(dǎo)致人們思維不清的主要原因，故不能選，D也不能說明原因。由第二段我們知道，睡眠不足是引起人們思維混亂的根本原因。
2. B.短文的第二段有交待：60%以上的成年人大約睡7-8小時。
3. D.判斷人們是否得到足夠的睡眠不是根據(jù)睡眠時間的長短而是人們是否精神煥發(fā)地去從事一天的工作與學(xué)習(xí)。
4. A. 14歲的孩子屬于early teenage. 他們的睡眠時間與成年人相同。故答案為A。
