情态动词表推测
(must/ can/ may/ could/ might)
一、肯定句
must＞may＞might/could
1. He must / may / might(could) come from
他肯定/可能/也许是美国人。
2. There is still light in his room. He must / may / might (could) be studying at this time.
他房间里还有灯光，他这时一定/可能/也许还在学习。
3. Tom isn’t in the classroom. He must / may / might (could) have gone to the library.
汤姆没在教室里，他一定/可能/也许到图书馆去了。
二、否定句
can’t, couldn’t不可能；mayn’t, mightn’t可能不
1. It’s snowing outside. He can’t / couldn’t / may not / mightn’t be on the playground.
外面在下雪，他不可能/可能不在操场上。
2. He knew nothing about the book. He can’t / couldn’t / may not / mightn’t have read it before.
三、疑问句
can，could
--- Can he be English?
--- No, He can’t be English. He must be American.
四、区别
(一) must; can’t 语气最强，基于观察到的迹象。
1. --- She looks very happy. She ___ have passed the exam.
--- I guess so. It’s not difficult after all.
A. should B. could C. must D. might (C)
2. She ____ have left school, for her bike is still here.
A. can’t B. wouldn’t C. shouldn’t D. needn’t (A)
(二) may; might; could 说话人不太确定的推测。
1. Helen ____ go on the trip with us, but she isn’t quite sure yet.
A. shall B. must C. may D. can (C)
2. --- Are you coming to Jeff’s party?
--- I’m not sure. I ____ go to the concert instead.
A. must B. would C. should D. might (D)
3. --- There were already 5 people in the car but they managed to take me as well.
--- It ____ a comfortable journey.
A. can’t be B. shouldn’t be C. mustn’t have been D. couldn’t have been (D)
(三) should 说话人的期盼
--- When can I come for the photos? I need them tomorrow afternoon.
--- They ___ be ready by 12:00.
A. can B. should C. might D. need (B)
(四) must用于肯定句；may/might用于肯定句、否定句；can用于否定句、疑问句；could用于肯定句、否定句、疑问句。
五、解题技巧
1. 判断句型：肯定句，否定句或疑问句。
2. 判断时间，确定使用什么时态。
3. 判断推测的强弱，确定使用哪个情态动词。
六、练习
表示推测的情态动词must、can, could, may, might及其否定式改写下列句子。
1. I am sure she is relaxing in her room.
She _____ be relaxing in her room.
2. Perhaps the plane arrived late, and that is why they are not here.
The plane _____ have arrived late, and that is why they are not here.
3. Maybe they lied to me about their adventure.
They ____ have lied to me about their adventure.
4. It is possible that Sam doesn’t like classical music.
Sam _____ like classical music.
5. I do not believe you failed the exam.
You _____ have failed the exam.
6. It is quite probable that Bill did not win the competition.
Bill _____ have won the competition.
7. I’m sure John is not forty-five yet.
John _____ be forty-five yet.
答案：
1. must 2. may/might/could 3. may /might/could
4. may not/might not 5 couldn’t/can’t 6. couldn’t/can’t 7. can’t
