4. ——我们一定要在六点以前到这儿吗？

——不，你们不必。

3. 这不可能是真的。

2. 他可能会来，但我想他不会来。

9. You don't       worry about her. She is much better now.

10. If you want to pass the exam,you       work harder.

7.       you tell me where the station is?

8. The train will leave at half past six,so I       get there fifteen minutes earlier.

5. You       give up smoking at once. It’s bad for your health.

6. Excuse me,        I ask you a question?

3. The book       be returned before Saturday.

4. —       I come in? —Yes,please.

1 .Nobody       live without air and water.

2. —       he speak Chinese? —Yes,a little.

10. From March 23rd 2013,anyone under the age of 14       go into Disney’s US parks alone.

   A. couldn’t   B. mustn’t

   C. needn’t   D. mightn’t

9. —Dad,must we wait until the light becomes green?

—Yes,I'm afraid we       . That’s the traffic rule.

   A. can   B. may   C. have to   D. need