1. 肯定的推测一般用must, should, may（might）或could（不用can），其中，must的语气最强，译为“肯定”、“准是”、“想必是”；should的语气次之，译为“很可能”、“应该”，指按常理推测；may（might），could的语气最弱，译为“也许”、“可能”。
①Helen _______ go on the trip with us but she isn’t quite sure yet. （2005年安徽卷）
A. shall B. must C. may D. can
②—I’ve taken someone else’s green sweater by mistake.
—It ___ Harry’s. He always wears green. （2005年广东卷）
A. has to be B. will be C. mustn’t be D. could be
③I have lost one of my gloves. I _______ it somewhere.（2005年北京春季卷）
A. must drop B. must have dropped
C. must be dropping D. must have been dropped
④If I ____ plan to do anything I wanted to ,I’d like to go to Tibet and travel through as much of it as possible. （2005年湖北卷）
A. would B. could C. had to D. ought to
1）语气不很肯定时，常用may not, might not或could not，译为“可能不”、“也许不”。
You might just as well tell the manufacturer that male customers ______ not like the design of the furniture. （2004年上海春季卷）
A. must B. shall C. may D. need
①—Do you know where David is? I couldn’t find him anywhere.
—Well. He ______ have gone far——his coat’s still here.（2005年湖北卷）
A. shouldn’t B. mustn’t C. can’t D. wouldn’t
②— Isn’t that Ann’s husband over there?
— No, it _______ be him I’m sure he doesn’t wear glasses. （2004年全国卷Ⅰ）
A. can’t B. must not C. won’t D. may not
Mr. Bush is on time for everything. How ______ it be that he was late for the opening ceremony？（2001年上海春季卷）
A. can B. should C. may D. must
4. 对已发生事情的肯定推测常用“must, may, might等+完成式”；否定推测常用“can, could, may, might等+完成式”。
①I was on the highway when this car went past followed by a police car. They _______ at least 150 kilometers an hour.（2005年重庆卷）
A. should have been doing B. must have been doing
C. could have done D. would have done
②He _______ have completed his work; otherwise, he wouldn’t be enjoying himself by seaside. （2005年北京卷）
A. should B. must C. wouldn’t D. can’t
③—Tom is never late for work. Why is be absent today?
—Something ________ to him. （2005年江西卷）
A. must happen B. should have happened
C. could have happened D. must have happened
④ My sister met him at the Grand Theatre yesterday afternoon, so he_____ have attended your lecture.（2000年上海卷）
A. couldn’t B. needn’t C. mustn’t D. shouldn’t
1. “should（ought to）+完成式”表示本应该做某事而实际上没有做。其否定式表示某种行为不该发生但却发生了。
①—I’ll tell Mary about her new job tomorrow.
— You________ her last week. （2004年福建卷）
A． ought to tell B． would have told
C． must tell D． should have told
②Oh, I’m not feeling well in the stomach, I _____ so much fried chicken just now. （2002年上海春季卷）
A. shouldn’t eat B. mustn’t have eaten
C. shouldn’t have eaten D. mustn’t eat
He paid for a seat, when he ______ have entered free. （2005年山东卷）
A. could B. would C. must D. need
You needn’t have watered the flowers, for it is going to rain.你本不需要浇花的，因为天就要下雨了。
— Catherine, I have cleaned the room for you.
— Thanks. You ______ it. I could manage it myself. （2005年福建卷）
A. needn’t do B. needn’t have done C. mustn’t do D. shouldn’t have done
①“The interest be divided into five parts, according to the agreement made by both sides，” declared the judge. （2004年重庆卷）
A. may B. should C. must D. shall
②—Excuse me, but I want to use your computer to type a report.
— You ______ have my computer if you don’t take care of it. （2004年湖南卷）
A. shan’t B. might not C. needn’t D. shouldn’t
③ — The room is so dirty. ______ we clean it?
— Of course. （2003年北京春季卷）
A. Will B. Shall C. Would D. Do
①John, look at the time. _______ you play the piano at such a late hour？ （2005年全国卷Ⅲ）
A. Must B. Can C. May D. Need
②Tom, you leave all your clothes on the floor like this！(2005年全国Ⅰ）
A. wouldn’t B. mustn’t C. needn’t D. may not
— Lucy doesn’t mind lending you her dictionary.
— She ______. I’ve already borrowed one. （2005年湖南卷）
A. can’t B. mustn’t C. needn’t D. shouldn’t
When he was there, he ___ go to that coffee shop at the corner after work every day.（1996年上海卷）
A. would B. should C. had better D. might
5. 表示经过努力而成功的某一次动作，只能用was/were able to，而不能用could。
The fire spread through the hotel very quickly but everyone _____ get out. （1997年全国卷）
A. had to B. would C. was able to D. could
①—Write to me when you get home.
— _______. （2001年北京春季卷）
A. I must B. I should C. I will D. I can
② — Could I call you by your first name？
—Yes, you ______. （1998年上海卷）
A. will B. could C. may D. might
1. Michael ______ be a policeman, for he is much too short.
A. needn’t B. can’t C. should D. may
2. I told Sally how to get here, but perhaps I ____ for her.
A. had to write it out B. must have written it out
C. should have written it out D. ought to write it out
3. Jack _____ yet, otherwise he would have telephoned me.
A. mustn’t have arrived B. shouldn’t have arrived
C. can’t have arrived D. needn’t have arrived
4. Sir, you ______be sitting in this waiting room. It is for women and children only.
A. mustn’t B. can’t C. won’t D. needn’t
5. A left-luggage office is a place where bags _______ be left for a short time, especially at a railway station.
A. should B. can C. must D. will
6. — Is John coming by train?
— He should, but he _____ not. He likes driving his car.
A. must B. can C. need D. may
7. It has been announced that candidates _______ remain in their seats until all the papers have been collected.
A. can B. will C. may D. shall
8. You can’t imagine that a well-behaved gentleman ______ be so rude to a lady.
A. might B. need C. should D. would
9. —Don’t forget to come to my birthday party tomorrow. —_______.
A. I don’t B. I won’t C. I can’t D. I haven’t
10. I didn’t see her in the meeting-room this morning. She____ at the meeting.
A. mustn’t have spoken B. shouldn’t have spoken
C. needn’t have spoken D. couldn’t have spoken
Key: C D B B Key: C Key: C A Key：A Key: B B D A Key: D C
Key：A Key: B Key: D A B Key: A B Key: C Key: A
Key：C Key：C C
1. B 从第二个分句“他太矮了”可以推知说话者持否定态度，needn’t意思是“没有必要”，与语境不符。
2. C 根据句意“我已经告诉她怎样到那儿，但是或许我应该给她写下来”可知，说话者含有“后悔、遗憾”的意味，应使用“情态动词+完成式”形式，“must+完成式”表示对过去的肯定推测，“should+完成式”才表示虚拟意义。
3. C 根据第二分句“否则的话他就会给我打电话了”可知“Jack肯定还没到”，“can’t+完成式”意思是“根本不可能”。
4. A 从第二分句可知，这是妇女和儿童专用候车室，因此你“不准”坐在这儿。mustn’t表示“禁止，不准”。
5. B can在此表示许可。
6. D 从后一句“他喜欢开车”可知说话者把握不大。must not不表示推测，can not的语气太绝对，意思是“根本不可能”。
7. D shall用于第二、三人称，表示说话人给对方的命令、警告、允诺、威胁等意思。
8. C should在此表示惊讶的感情色彩，意思是“竟然”。
9. B 对祈使句的肯定回答用I will；否定回答用I won’t。
10. D 根据句意“我今天上午在会议室没见到她”， 所以“她根本不可能在会上发言”。表示“根本不可能”用can’t/couldn’t have done形式。