Do you know why you sleep? You may think it’s because you’re tired. Or perhaps you’ve been

Do you know why you sleep? You may think it’s because you’re tired. Or perhaps you’ve been told sleep is good for you. Yet no one knows exactly why or how people sleep.
Until the early 1950s, most scientists thought the body and brain rested during sleep. Then a scientist watched people sleep. He noticed that during periods of between 5 and 30 minutes each, sleepers’ eyes made rapid movements, as if they were watching something. He called these periods REM sleep, for Rapid Eye Movement. Periods when sleepers’ eyes did not move he called non-REM sleep.
Whenever the scientist woke people during REM sleep, they were having vivid dreams. Measurements showed that sleepers’ pulses（脉搏）went up quickly during REM sleep. Their breathing, heartbeat, and the blood going to the brain also increased. Far from being a time of rest, REM sleep is a time when the body is hard at work. Scientists still don’t know the reason for this. Some believe REM sleep makes learning easier. Babies spend a lot of time in REM sleep. Because of this, some scientists believe that REM sleep helps the brain grow. Others think REM sleep is a time for the brain to empty the day’s garbage.
One thing all the scientists agree on is that sleep is necessary. Without enough sleep, people make mistakes. Most major car accidents happen during the early morning hours, when people are sleepiest.
【小题1】During REM sleep, a person’s breathing and heartbeat .A．stopB．increaseC．decreaseD．stay the same【小题2】Which word in paragraph（段落）3 means “colorful and lively”?A．easierB．emptyC．vividD．quickly【小题3】Which paragraph tells what happens when people don’t get enough sleep?A．1B．2C．3D．4【小题4】What is the main idea of the article?A．REM sleep helps the brain grow.B．REM sleep has been watched and recorded by scientists.C．REM sleep is a time to empty the day’s garbage.D．REM sleep is an active time when the body is hard at work.【小题5】You can decide from the article that REM sleep .A．has a restful effect on peopleB．can be avoided with lots of sleepC．is something that all people experienceD．is something that all scientists agree onB

(答案→)B 解析：【小题1】本文第三段提到人在REM睡眠阶段，一个人的呼吸和心跳上升，故本题选B。【小题2】第三段第一句的含义为人在REM睡眠阶段，人会做五颜六色，多姿多彩的梦，vivid表示此意，故本题选C。【小题3】本文第四段提到人们没有得到足够的睡眠，人们可能会犯错误，如车祸，故本题选D。【小题4】本文第二段提到科学家观察和记录了人们的REM睡眠阶段的有关情况，为本文的主要内容，故本题选B。【小题5】本文第二段提到人们在REM睡眠阶段，人的身体和大脑会得到休息的效果，故本题选A。

这个解释是对的