1、ModalVerbs,情態(tài)動(dòng)詞 can, could, may,might,must表推測(cè)的用法：,情態(tài)動(dòng)詞中的can, could, may, might, must都表推測(cè)。其中must的可能性最大，can / could次之，may / might最小。具體用法如下：1. must的用法（1）表示推測(cè)“可能性”時(shí)，意思是“一定、準(zhǔn)是”，語(yǔ)氣較肯定，較有把握。He must be American. = It is certain that he is American. 他準(zhǔn)是個(gè)美國(guó)人。,（2）must表推測(cè)只能用于肯定句。 如表示“一定不、肯定不”的意思時(shí)，應(yīng)用cant, 如詢(xún)問(wèn)某種可

2、能時(shí)，應(yīng)用can。He must know my address. 他肯定知道我的地址。 （一定） He cant know my address. 他肯定不知道我的地址。 （一定不）Can he know my address? 他知道我的地址嗎？ （詢(xún)問(wèn)可能性）,（3）must表示推測(cè)時(shí)，可以推測(cè)現(xiàn)在/正在發(fā)生的動(dòng)作/過(guò)去發(fā)生的動(dòng)作。He must have a car now. （現(xiàn)在）他一定有輛小汽車(chē)。He must be doing his exercises in the classroom.（正在進(jìn)行）他一定在教室里做練習(xí)。He must have finished the wo

3、rk.（過(guò)去發(fā)生）他一定已完成了工作。注：must表示推測(cè)時(shí)很少用于將來(lái)的情況。一般不用He must come tomorrow.可用Its certain / Im sure that he will come tomorrow.,（4）在反意疑問(wèn)句中，當(dāng)附屬部分含有表示推測(cè)意義的must時(shí)，疑問(wèn)部分的助動(dòng)詞應(yīng)與must后面的動(dòng)詞在非推測(cè)情況下的用法保持一致。 He must be a worker, isnt he? （現(xiàn)在）他準(zhǔn)時(shí)個(gè)工人，是嗎？ You must have learned English for many years, havent you? （完成時(shí)）你一定學(xué)了好多年

4、英語(yǔ)，是嗎？比較： It must have rained last night, didnt it? （過(guò)去）昨晚一定下雨了，是不是？He must have arrived by yesterday morning, hadnt he?,2. can / could的用法（1）can表示推測(cè)“可能性”時(shí)，往往用于否定句或疑問(wèn)句。Cant“一定不”，can在疑問(wèn)句中意思是“會(huì)、可能”。He cant be at home. = It is impossible that he is at home. 他一定不在家。（2）can /cant+ have done，表示對(duì)過(guò)去發(fā)生的動(dòng)作進(jìn)行推測(cè)。

5、He cant have gone to Shanghai for I saw him a minute ago. 他不可能去了上海，我剛才還看見(jiàn)他。Its so late. Where can she have gone? 天晚了，她可能去哪兒了呢？,（3）could 還可以用于表示客氣、委婉、禮貌的請(qǐng)求語(yǔ)氣。 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，表虛擬語(yǔ)氣 I could have done it well，but I was

6、nt so careful then .,3. may和might的用法（1） may, might表示推測(cè)“可能性”時(shí)，意思是“可能”、“也許”He may / might be American. = It is possible that he is American.他可能是個(gè)美國(guó)人。注：might不表示過(guò)去時(shí)態(tài)，只是語(yǔ)氣上比may更委婉，表示的可能性更小。（2）may, might表推測(cè)時(shí)，可以用于否定句，意思是“可能不、也許不”，但不用于疑問(wèn)句。He may / might not be at home. 他也許不在家。,（3）may, might可以推測(cè)現(xiàn)在正在發(fā)生的動(dòng)作或過(guò)去發(fā)

7、生的動(dòng)作。He may / might be sleeping now. The boy may / might not be watching TV at home. 這個(gè)男孩可能沒(méi)在家看電視These students may / might have seen the film before.（過(guò)去） 這些學(xué)生以前可能看過(guò)這部電影。,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

8、. 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 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.

9、can; can; mustC. can; mustnt; must D. must; mustnt; can 5. 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 it can be,6. I saw Mary in the library yesterday.-You_ her. She is still abroad.A. mustnt see B. cant have seen C. mustnt have s

10、een D. couldnt see 7. 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.A. must change B. should have changedC. must have changed D. would have changed,9. Sue_ come together with

11、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 miss,情態(tài)動(dòng)詞+have+done” 表“本來(lái)應(yīng)該” 使用情況分析,一、should have done過(guò)去本來(lái)應(yīng)該 （而實(shí)際上并沒(méi)有) should not have done

12、 本不應(yīng)該 而實(shí)際上卻已經(jīng)” 如：1、We should have studied last night, but we went to the concert instead . 我們昨晚本應(yīng)學(xué)習(xí)的，但我們卻去看音樂(lè)會(huì)了。（實(shí)際上沒(méi)有學(xué)習(xí)）,二、could have done 它表示“過(guò)去本來(lái)能夠” 實(shí)際上沒(méi)能做。 如1、I could have run 100 metres in 12 seconds. 我本來(lái)能用12秒鐘完100米的.（實(shí)際上沒(méi)能） 2、If you could have finished the task in time，you could have been prom

13、oted. 如果你當(dāng)時(shí)能如期完成那任務(wù)的話(huà)，你可能已提升了（實(shí)際上沒(méi)有被提升）,三、need not have done 它表示過(guò)去已做的事，事實(shí)上沒(méi)有必要。 如，1、I need not have got up so early . 我本來(lái)不必要那么早起床的（事實(shí)上早已起床） 2、I need not have waited for the train for an hour. 我本來(lái)不必要等一個(gè)小時(shí)的火車(chē)。 （事實(shí)上已經(jīng)等了一個(gè)小時(shí)） 問(wèn)題:,would have done 在什么情況下使用呢?,四、would have done 用在虛擬語(yǔ)氣中 表示與過(guò)去事實(shí)相反之假設(shè)的結(jié)果，常與if

14、的條件句連用。 1、 I would have helped you if I had known of your difficulties . 要是我當(dāng)時(shí)知道你們的窘境，我就會(huì)幫助你了（而實(shí)際上沒(méi)有幫助你） 2、If it hadnt rained yesterday, we would have gone out for a walk .假如昨天沒(méi)下雨，我們就去散步了。 （實(shí)際上沒(méi)有去）。,Practice,1.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 arriving,2. If he had been here yesterday, he _ this pop star. A. would meet B. would have met C. met