3. C 　参见第三段第三句“You would feel tired if you didn't.”

2. D 　第二段后半部分作了说明：“The best conditions for sleep are good health and meals neither too big nor too small. No worries and a comfortable place are important，too.”

1. D 　参见第二段第三句“They are not sure what causes sleep.”

4. The best title for the passage is ___________.

　　 A. How can You Get a Good Sleep

　　 B. The Strangeness of Sleep

　　 C. What Happens During Sleep

　　 D. The Causes of Dream

参考答案

3. You would feel tired during sleep if you ___________.

　　 A. moved too often　　 B. slept on your back

　　 C. didn't move　　　　　 　　 D. went to sleep late

2. The best conditions for sleep are ___________.

　　 A. good health

　　 B. a meal neither too big nor too small

　　 C. no worries

　　 D. good health，limited meal，no worries and a good place

1. Sleep puzzles scientists because they are not certain ___________.

　　 A. why one can't fall asleep　　 B. why one wakes up

　　 C. both A and B　　　　　　　　　　　 　　 D. what causes sleep

5. T　 由E段第一句可知。