1、情态动词情态动词 can,could,may,might,must表推测表推测的用法的用法 情态动词中的情态动词中的can,could,may,might,must都表推测。其中都表推测。其中mustcan/couldmay/might.must的用法的用法（1）表示推测）表示推测“可能性可能性”时，意思是时，意思是“一一定、准是定、准是”，语气较肯定，较有把握。，语气较肯定，较有把握。He must be American.他准是个美国人。他准是个美国人。（2）must表推测只能用于肯定句表推测只能用于肯定句。如表示如表示“一定不、肯定不一定不、肯定不”的意思时，的意思时，应用应用cant,
2、如询问某种可能时，应用如询问某种可能时，应用can。He must know my address.他肯定知道我的地址。（一他肯定知道我的地址。（一定）定）He cant know my address.他肯定不知道我的地址。（一定不）他肯定不知道我的地址。（一定不）Can he know my address?他知道我的地址吗？（询问可能性）他知道我的地址吗？（询问可能性）（3）must表示推测时，可以推测现在表示推测时，可以推测现在/正在正在发生的动作发生的动作/过去发生的动作过去发生的动作。He must have a car now.（现在）他一定有辆小汽车。（现在）他一定有辆小汽车。
3、He must be doing his exercises in the classroom.（正在进行）他一定在教室里做练习（正在进行）他一定在教室里做练习。He must have finished the work.（过去发生）他一定已完成了工作。（过去发生）他一定已完成了工作。注：注：must表示推测时表示推测时很少用于将来的情况很少用于将来的情况。一般不。一般不用用He must come tomorrow.可用可用Its certain/Im sure that he will come tomorrow.（4）在反意疑问句中，当附属部分含有表示推测意）在反意疑问句中，当附属部分
4、含有表示推测意义的义的must时，疑问部分的助动词应与时，疑问部分的助动词应与must后面的动后面的动词在非推测情况下的用法保持一致。词在非推测情况下的用法保持一致。He must be a worker,isnt he?（现在）他准时个工人，是吗？（现在）他准时个工人，是吗？You must have learned English for many years,havent you?（完成时）你一定学了好多年英语，是吗？（完成时）你一定学了好多年英语，是吗？比较：比较：It must have rained last night,didnt it?（过去）昨晚一定下雨了，是不是？（过去）昨
5、晚一定下雨了，是不是？He must have arrived by yesterday morning,hadnt he?can/could的用法的用法（1）can表示推测表示推测“可能性可能性”时，往往用于否时，往往用于否定句或疑问句。定句或疑问句。Cant“一定不一定不”，can在疑问在疑问句中意思是句中意思是“会、可能会、可能”。He cant be at home.=It is impossible that he is at home.他一定不在家。他一定不在家。（2）can/cant+have done，表示对过去发生，表示对过去发生的动作进行推测。的动作进行推测。He cant
6、 have gone to Shanghai for I saw him a minute ago.他不可能去了上海，我刚才还看见他。他不可能去了上海，我刚才还看见他。Its so late.Where can she have gone?天晚了，天晚了，她可能去哪儿了呢？她可能去哪儿了呢？（3）could 还可以用于表示客气、委婉、还可以用于表示客气、委婉、礼貌的请求语气。礼貌的请求语气。Excuse me,could you tell me the way to the bus station?Could you help me?（4）could have done 本能做但未做，表虚拟语
7、气本能做但未做，表虚拟语气 I could have done it well，but I wasnt so careful then.may和和might的用法的用法（1）may,might表示推测表示推测“可能性可能性”时，意时，意思是思是“可能可能”、“也许也许”He may/might be American.=It is possible that he is American.他可能是个美国人。他可能是个美国人。注：注：might不表示过去时态，只是语气上比不表示过去时态，只是语气上比may更委婉，表示的可能性更小。更委婉，表示的可能性更小。（2）may,might表推测时，可以用
8、于否定句，表推测时，可以用于否定句，意思是意思是“可能不、也许不可能不、也许不”，但，但不用于疑问不用于疑问句句。He may/might not be at home.他也许不在家。他也许不在家。（3）may,might可以推测现在正在发生的动可以推测现在正在发生的动作或过去发生的动作。作或过去发生的动作。He may/might be sleeping now.The boy may/might not be watching TV at home.这个男孩可能没在家看电视这个男孩可能没在家看电视 These students may/might have seen the film be
9、fore.（过去）（过去）这些学生以前可能看过这部电影。这些学生以前可能看过这部电影。u Choose the best answers:1.I thought you_ like something to read.So I have brought you some books.A.ought B.might C.would D.must 2.That man must be Sarahs husband.-No,he_ be her husband.She is still single.A.cant B.mustnt C.may not D.ought to 3.Peter _come
10、 with us tonight,but he isnt very sure.A.must B.may C.can D.will 4.What_ it be?-It_ be a mail box,for it is moving.It_ be a car.A.can;cant;must B.can;can;mustC.can;mustnt;must D.must;mustnt;can5.Look,someone is coming.Guess_.-Jack.Hes always on time.A.who can it be B.who he mayC.who he can be D.who
11、it can be6.I saw Mary in the library yesterday.-You_ her.She is still abroad.A.mustnt see B.cant have seen C.mustnt have seen D.couldnt see7.David,you _play with the valuable bottle,you_ break it.A.wont;cant B.mustnt;mayC.shouldnt;must D.cant;shouldnt 8.Susan refuses to marry Jack now.She _her mind.
12、A.must change B.should have changedC.must have changed D.would have changed9.Sue_ come together with us tonight,but she isnt very sure yet.A.must B.may C.need D.will 10.Aunt Margaret_ the train,otherwise she would have arrived here by now.A.must have missed B.should have missedC.had missed D.might m
13、isscould have done 过去本来能够过去本来能够”实际上没能做实际上没能做 I could have run 100 metres in 12 seconds.我本来能用我本来能用12秒钟完秒钟完100米的米的.（实际上没能）（实际上没能）If you could have finished the task in time，you could have been promoted.如果你当时能如期完成那任务的话，你可能已提如果你当时能如期完成那任务的话，你可能已提升了（实际上没有被提升）升了（实际上没有被提升）情态动词情态动词+have+done”表表“本来应该本来应该”sho
14、uld have done 过去本应该做而没做过去本应该做而没做 should not have done 本不应该本不应该 而实际上却已经而实际上却已经”We should have studied last night,but we went to the concert instead。You shouldnt have climbed that hill，it is too dangerous.need not have done 它表示过去已做的事，事实上没有必要。它表示过去已做的事，事实上没有必要。(不需要做而做了）不需要做而做了）I need not have got up so
15、 early.我本来不必要那么早起床的（事实上早已起床）我本来不必要那么早起床的（事实上早已起床）I need not have waited for the train for an hour.我本来不必要等一个小时的火车。（事实上已经我本来不必要等一个小时的火车。（事实上已经等了一个小时）等了一个小时）Practice1.Mr White _ at 8:30 for the meeting,but he didnt turn up.A.should have arrived B.should arrive C.should have had arrived D.should be arri
16、ving 1.I can run fast.(否定句)2.You must return the book now.（一般疑问句并且否定回答）3.He can play basketball well.（一般疑问句）4.They must take the books out of the room.（否定句）5.Need he go to school tomorrow.(肯定否定回答）6.Daniel must watch TV every evening.(改为否定句)7.I cant do my homework every day.(改为肯定句)8.Youll need your book and pen.(改为否定句)
