1、情态动词表推测,Modal Verbs,一、常用于表推测的情态动词有： must/can/could/will/would/may/might/should/ought to 二、表推测的三种句式：1. 在肯定句中一般用must，can/could，may/might，程度逐渐减弱。 a. He must/may/might know the answer to this question. b. You have worked all this week. You must be tired.2. 在否定句中用cant/couldnt (不可能)，may not/ might not(可能不
2、)。,a. It cant /couldnt be the headmaster. He has gone to America. b. He may not/might not know the scientist.3. 在疑问句中，一般只使用can/could。 a. Could he have finished the task? b. Can he be at home now?三、表推测的三种时态1.对现在和一般情况的推测，用“情态动词V原” a. They must be in the classroom now. b. Something must be wrong with t
3、he TV set. c. He may not be at home at this time.,2.对正在进行的动作或事情的推测，常用“情态动词+be doing sth” a. The light in the teachers office is still on.Miss Gao must be working. b. He must be listening to the radio now.3. 对过去或已经完成事情的推测，常用“情态动词+have done sth.” a. Peter may/might have been hurt in the car accident.
4、b. He must have finished his homework yesterday, hasnt he? c. Can/Could he have gotten the book?,注：情态动词should/ ought to 表推测时， 意为“想必会，理应”但与“have+过去分词”连用时，则又可构成虚拟语气，意为“本应该做某事却没有做”。例如： a. Its seven oclock. Jack should/ought to be here at the moment. b. She should/ought to have attended your birthday pa
5、rty, but she had to look after her mother in hospital.四、几组表推测的情态动词用法,1. must have done 表对已经发生的事情的推测，意为“一定，想必”，在句子中表示的是一种肯定的推测。这种结构一般只用于肯定句，其否定形式为：cant(couldnt) have done，表示“不可能，肯定不会”。 a. He didnt hear the phone. He must have been asleep. b. They cant have gone out, because the light on.2. can（could）
6、 have done 表对过去的时间里可能发生的事情的推测，一般只用于否定句和疑问句。,a. He cant have finished the work so soon. 用于肯定句中，常用来表示本来可以完成而实际未完成的动作。 b. We could have walked to the station, it was so near.3. may(might) have done 1) 表对已经发生的事情不太肯定的推测，意为“可能已经，或许已经” 2) 虚拟用法表可以做，但却没有做。 a. If we had taken the other road, we might have arrived earlier. b. He might have given you more help, he,was very busy.4. neednt have done 指实际上做了本不要做的事情，意为“本来不必”。 a. There was plenty of time. She neednt have hurried. b. You neednt have told him the news.,
