根据句意及首字母或汉语提示完成句子。

1. You will fail in the Chinese exam u _____ you study  hard.    

2. Everyone can make mistakes. Don't l _____ at him.    

3. Look!  It says "No P _____ " on the sign.  You'd better drive your car away.

4. The air in the morning is very f _____.    

5. He d _____ himself as a clown at the costume party.    

6. Tell the t _____, or I won't believe you.    

7. We should try our best to protect e _____ animals.    

8. Some of the rivers have become p _____.They are dirty now.

9. The boy looked w _____ because he couldn't find his keys.

10. Our teachers asked us to do our homework as c _____ as we can.