选用适当的情态动词填空。

(can, may, must, can't, mustn't. )

1．________ you speak French? No, I ________, but Mr. Black ________.

2．________ I use your knife? Certainly.

3．________ we go out and play football now? No, you ________. You ________ finish your

     homework first.

4．She ________ hear you clearly. Please speak a little louder.

5．How long ________ I keep this book? You ________ keep it for two weeks.