1. 选择方框里合适的词组填空，并注意形式的变化。

a piece of; keep…away; more than; every time; be good for

1. （1） Doing eye exercises your eyes.

3. （2） He watches TV two hours at the weekend.

5. （3） — How long does Nancy dance?

   — Less than two hours.

7. （4） We all know an apple a day the doctor.

9. （5） Nancy is nibbling(啃)some bread while drawing a picture.