完形填空 先通读下面的短文，掌握其大意，然后在每小题所给的四个选项中，选出可以填入空白处的最佳选项。(本大题共10分，每小题1分)
Up to two-thirds of children don’t get as much sleep as they should do and this can make them nervous and slower at school, researchers say.
So        should young people sleep each night? The answer is between 8 and 10 hours. If you don’t get enough sleep at night, you’ll have      energy the next day.
But the researchers say many children have missed out on 4,500 hours of sleep by the time they are 7 years old. They say that children miss sleep because they have TVs and computers in their rooms and         parents don’t read to their younger children at night any more. The traditional “bedtime story” helps children to relax and fall asleep       . Children with TVs and computers in their bedrooms are more likely to sleep badly and to get less than 8 hours sleep. Even       one hour’s sleep a night can mean that children do less well at school.
German scientists think that your        keeps working while you are asleep. To show that they were       , they gave two groups of people a problem to work out. One group went to sleep and the other group stayed      . The result? The people who slept worked out the answer more quickly, suggesting that their brains had been trying to     the answer while the people were asleep. So, make sure you get enough sleep tonight,        you’ll be at your best tomorrow．

A．how much B．how many C．how long D．how often

A．more B．less C．few D．little

A．proud B．free C．poor D．busy

A．peacefully B．carefully C．happily D．sadly

A．losing B．lost C．loser D．loss

A．head B．brain C．heart D．thought

A．perfect B．bright C．right D．great

A．awake B．alive C．asleep D．absent

A．think over B．open up C．find out D．put down

A．or B．but C．if D．and