问题补充：
E
After a busy day of work and play, the body needs to rest. Sleep is necessary for good health. During this time, the body recovers from the activities of the day. The rest that you get while sleeping makes it possible for your body to prepare itself for the next day.
There are four levels of sleep, each being a little deeper than the one before. As you sleep, your body relaxes little by little. Your heart beats more slowly, and your brain slows down. After you reach the fourth level, your body shifts(变换) back and forth from one level to the other.
Although your mind slows down, you will dream from time to time. Scientists who study sleep point out that when dreaming occurs, your eyeballs begin to move more quickly (although your eyelids are closed). This stage of sleep is called REM, which stands for rapid eye movement.
If you have trouble falling asleep, some people recommend(建议) breathing very slowly and very deeply. Other people believe that drinking warm milk will make you drowsy. There is also an old suggestion that counting sheep will put you to sleep.
49. During REM,
A. you move restless B. you start dreaming
C. your mind stops working D. your eyeballs move quickly
50. A good title for this text might be
A. Dreams B. Sleep C. Good Health D. Work and RestD
答案：
(答案→)D
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