根据短文内容和所给首字母，在空格处填入一个适当的词，使短文意思完整。

     Have you heard such an old English saying? It (1)s             that we must go to bed early and get up

early. Then we should be (2)h             and clever.

     This is (3)t            . The body must have enough sleep to be healthy. Children of teenagers (青少年)

should have ten (4)h             sleep every night. If they don't have (5)e            sleep, they can't do their

work very (6)w           .

     The body also needs (7)e            . Walking, running, jumping, swimming and playing games are all

exercise. Exercise keeps the body (8)s            . Exercise also keeps the blood (血) moving around inside

the body. It is very (9)i            because our blood takes food to all parts of our body. The (10)h           

 also needs blood, exercise helps us to think better!