1 . 选词填空。
1. My mother is ill, so I ________(have to/ must)stay home to look after her.
2. He ________(can’t/ mustn’t)be Tom. Tom has gone to London, you know.
3. It’s dark outside. Besides, it’s raining heavily. So, you ________(had better/ might)go home with me.
4. In today’s information age, the loss of data ________(can/must)cause serious problems for a company.
5. It’s strange that he ________(should/ must)have taken the books without the owner’s permission.
6. Samuel, the tallest boy in our class, ________(can/should)easily reach the books on the top shelf.
7. My room is in a mess, but I ________(needn’t/ shouldn’t)clean it before I go out tonight. I can do it in the morning.

2 . 选词填空mustn’t/needn’t
1. Books _________be taken out of the library without permission.
2. John is ill and he__________ go to school today.