何明博

A strange thing happens to nearly everybody at night. They turn off the lights，pull up the covers and close their eyes. Six or seven sleeping hours later，they wake up again. Strange，isnt it？

Sleep puzzles scientists. Scientists and doctors would rather talk about why one cant fall asleep. They are not sure what causes sleep. 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. They advise against two in bed.

Strange things happen during sleep. For example，they move often. You would feel tired if you didnt. You also dream. Part of your brain is still awake when you dream. Dreaming happens when the memory and imagination in parts of your brain are still awake. Experiments have shown most of us dream in color. Bad dreams may be caused by stomachache.

Dont worry if you dream. Some great stories and poems were begun while their writers slept.

鞏固提高

1. Sleep puzzles scientists because they are not certain____________.

A. why one cant fall asleep ? ? B. why one wakes up

C. both A and B D. what causes sleep

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

3. You would feel tired during sleep if you____________.

A. moved too often B. slept on your back

C. didnt move D. went to sleep late

Keys：1-3 DDC