13. He had known the matter before you told him, so you _________ have told it to him.

　　 A. mustn't　　 B. can't　　 C. needn't　　 　　　　　　　 D. shouldn't

12. ---- That must be a mistake.　　　　　　　　　 ---- No .it _________ be.

　　 A. can't　　 　 B. isn't able to　 　 　C. can　　 　 D. was able to

11. You must have seen him off yesterday, _________?

　　 A. haven't you　　　 B. didn't you　　　　　　 C. mustn't you　　 　D. needn't you

10. You must be fifty, ________?

　　 　　　 　A. mustn't you　　 B. needn't you　　　　　　 C. aren't you　　　 D. mnyn't you

9. Since the ground is white, it _________ last night.

A. had snowed　　 B. must have snowed　　 C. must be snowing　　 D. must have been snowing

8. They _________ the plane, or perhaps they have been prevented from coming for some reason.

　 A. can have missed　　 B. may have missed　　　　 C. can have lost　　　 D. may have lost

7. "We didn't see him at the lecture yesterday. "　　　　　　　　 　　 "He _________ it. "

　　 A. mustn't attend　 B. can't have attended　 C. would have not attended 　D. needed have attended

6. ---- _________ this book be yours?　　　　 ---- No, it ________ not be mine. It ________ be his.

　　 A. Can, must, may　　 B. May, might, must　　　　　　　 C. Can, may, must 　D. Must, can, may

5. I went to the doctor's yesterday, I had to wait for half an hour before he ________ see me.

　　 A. can　　 B. may　　 C. might　　 D. could

4. He was a good swimmer so he _________ swim to the river bank when the boat sank.

　　 A. could　　 B. might　　 C. should　　 D. was able to