1. 根据语境从方框中选择恰当的情态动词填空，每词限用一次

must, can, needn't, mustn't, have to

1. （1） — I come in?

   —Yes, please.

3. （2） We should be quiet in the theatre. Wespeak loudly.
5. （3） —Must I return this book to the library today, Mrs Brown?

   —No, you

7. （4） —Must I stay with you, Grandpa?

   —No, you don'tYou can go swimming with your friends.

9. （5） Webe careful when we cross the road.