用所给词的适当形式填空

1. Please listen to me          (careful), I have something important to tell you.

2. The          ( twelve) lesson is more difficult.

3. The girl is old enough to look after         (she).

4. The supermarket is usually _________ (crowd) on Sundays.

5. A cup is used for ___________(drink) water.

6. Lily is            (help). He often helps others.

7. I think the most useful           (invent) is the telephone.

8. How many           (factory) are there in our country?

9. Though you failed this time, don't give up______ (study) .

10. I am afraid to hurt their __    ___ (feel).