3．阅读下面短文，掌握其大意，然后从A、B、C、D四个选项中选出最佳选项．
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（31）C should young people sleep each night？The answer is between 8 and 10 hours．
If you don't get enough sleep at night，you'11 have（32）Benergy the next day．
But the researchers say many children have missed out on 4，500 hours of sleep（33）Athe time they are 7 years old．They say that children miss sleep because they have TVs and computers in their rooms and（34）D parents don't read to their younger children at night any more．The traditional"bedtime story"helps children to relax and fall asleep（35）A．Children with TVs and computers in their bedrooms are more likely to sleep badly，and to get less than 8 hours sleep．Even losing one hour's sleep a night can mean that children do less well at school．
German scientists think that your （36）Bkeeps working while you are asleep．To show thatthey were （37）C，they gave two groups of people a problem to work out．One group went tosleep and the other group stayed（38）A．The result？The people who slept worked out the answer more quickly，suggesting that their brains had been trying to（39）Cthe answer while the people were asleep．So，make sure you get enough sleep tonight，（40）Dyou'll be at your best tomorrow．
| 31．A．how much | B．how many | C．how long | D．how often |
| 32．A．more | B．1ess | C．few | D．1ittle |
| 33．A．by | B．at | C．on | D．during |
| 34．A．proud | B．free | C．poor | D．busy |
| 35．A．peacefully | B．carefully | C．happily | D．sadly |
| 36．A．head | B．brain | C．heart | D．thought |
| 37．A．perfect | B．bright | C．right | D．great |
| 38．A．awake | B．alive | C．asleep | D．absent |
| 39．A．think over | B．open up | C．find out | D．put down |
| 40．A．or | B．but | C．if | D．and． |
