《情态动词use》PPT课件.ppt

Unit13 Grammar,情态动词must, can, could, may, might表推测的用法：,情态动词中的must, can, could, may, might都表推测。其中must的可能性最大，can / could次之，may / might最小。具体用法如下： 1. must的用法 （1）表示推测“可能性”时，意思是“一定、准是”，语气较肯定，较有把握。 He must be American. = It is certain that he is American. 他准是个美国人。,2）must表示推测时，可以推测现在/正在发生的动作/过去发生的动作。 Must +动词原形 Must be doing Must have done He must have a car now. （现在）他一定有辆小汽车。 He must be doing his exercises in the classroom.（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。,（2）must表推测只能用于肯定句。如果要表示“一定不、肯定不”的意思时，应用cant 肯定：must do 否定：cant do 肯定：must have done 否定：cant have done 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） You must have met him before . You cant have met him before .,3)Must not 表示禁止，是说话人强有力的劝告，意为“决不可以”“不准”“不允许” You mustnt park your car there . You mustnt talk to her like that .,4)回答以must提问的句子，用如下肯定或否定形式作答： Must we clean all the rooms? Yes, you must . No, you dont have to. No, you neednt.,5）在反意疑问句中，当附属部分含有表示推测意义的must时，疑问部分的助动词应与must后面的动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？ It must have rained last night, didnt it? （过去）昨晚一定下雨了，是不是？ 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？,2. can / could的用法 （1）can表示推测“可能性”时，往往用于否定句或疑问句。Cant“一定不”，语气很肯定。can在疑问句中意思是“会、可能”。 He cant be at home. 他一定不在家。 Can he know my address?他知道我的地址吗？ （2）can /cant后可接进行时/完成时，表示对现在发生的动作或过去发生的动作进行推测。 Cant be doing / cant have done They cant be reading in the library now . He cant have gone to Shanghai for I saw him a minute ago. Its so late. Where can she have gone?,（3）在反意疑问句中，当陈述部分含有表示推测意义的cant时，疑问部分的助动词应与cant后面的动词在非推测情况下的用法保持一致. He cant be a teacher, is he? 他不是教师，是吗？ She cant have finished her homework, has she? 她一定没有完成家庭作业，是不是？,3. may和might的用法 （1） may, might表示推测“可能性”时，意思是“可能”、“也许”，语气没有 must肯定。 He may / might be American. 他可能是个美国人。 注：might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。 （2）may, might表推测时，可以用于否定句，意思是“可能不、也许不”，但不用于疑问句。 He may / might not be at home. 他也许不在家。,（3）may, might可以推测现在正在发生的动作或过去发生的动作。 May/might + 动词原形 May/might be doing May/might have done I think we should take raincoat with us, it may rain. (将来)我想我们应该带上雨衣，可能要下雨了。 He may / might be sleeping now. （现在）他可能正在睡觉。 These students may / might have seen the film before.（过去）这些学生以前可能看过这部电影。,一. Choose the best answers to complete the following sentences: 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. can; can; must C. 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 may C. 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 seen D. couldnt see 7. David, you _play with the valuable bottle, you_ break it. A. wont; cant B. mustnt; may C. shouldnt; must D. cant; shouldnt,8. Susan refuses to marry Jack now. She _her mind. A. must change B. should have changed C. must have changed D. would have changed 9. 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 missed C. had missed D. might miss,3、I should have thought of that 这一点我应该想到的。（但实际上没想到） 4、They shouldnt have left so soon . 他们不应当走得那么早。（但实际上还是走了） 5、He shouldnt have said such a thing .他当时不应该说那种话。（但已经说了） 在表示推测时，它表示的是“大概已经，或许已经”的意思。 如，1、The train should have already left.火车大概已经开走了。 2、Time is up , you should have finished your exercises . 时间已到，你们可能已经做完作业了。,情态动词+have+done”的使用情形分析,一、should have done/ should not have done 它们分别表示“过去本来应该（已经）（而实际上并没有）”/“过去本不应该（已经）而实际上却已经” 如：1、We should have studied last night, but we went to the concert instead . 我们昨晚本应学习的，但我们却去看音乐会了。（实际上没有学习） 2、If he had joined us , we should have had a more enjoyable time . 如果他加入我们的活动，我们就可以玩得更开心了。（实际上没那么开心，由于他没加入我们的活动）,二、would have done 它表示的是与过去事实相反之假设的结果，意思是“当时就会了”而实际上没有 如，1、 I would have helped you if I had known of your difficulties . 要是我当时知道你们的窘境，我就会帮助你了（而实际上没有帮助你） 2、If it hadnt rained yesterday, we would have gone on excursion .假如昨天没下雨，我们就去远足了。（实际上没有去）。 在表示推测时，它表示“过去大概是，似乎、可能”如 1、I suppose the writer would have been about thirty when he published his first work . 我想这位作家出版第一部作品时，大概是30岁左右。,三、must have done 它表示“过去一定了且结果延续到现在”是一种对过去发生的事进行推测。如， 1、No one answers the phone call,they must have already gene out ,没人接电话，他们一定已经出去了。 2、They must have arrived by now.现在他们想必已经到达。 3、You must have known what he wanted .你当时一定知道他要什么。 4、Where is my pen? I must have lost it . 我的钢笔在哪？我肯定把它弄去了。,四、cannot have done/couldnt have done 这两个形式表示“过去应该不可能做”如， 1、He cannot have promised it . 他应该不会答应那种事。 2、John is very clever . He cannot have told his son to do that . 约翰是很聪明的，他应该不会叫他儿子那样做。 3、He couldnt have said such a thing . 他应该不会说出这样的事。,五、 cant have done 它表示“过去不可能做“。如 1、she cant have gone to school , we have no school today.她不可能到学校去，今天我们学校放假。 2、He cant have finished the work so soon .这项工作他不可能完成得这样快。 3、Jack doesnt work hard at all. He cant have passed this English examination . 杰克学习根本不用功。他不可能通过这次英语考试。,七、could have done 它表示“过去本来能够“ 实际上没能做。如 1、I could have run 100 metres in 12 seconds.我本来能用12秒钟完100米的。（实际上设能） 2、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，你可能已提升了（实际上没有被提升） 3、I could have laughed to hear him talk like that.听他那样讲话，我差点笑出声来。 4、In those circumstances we could have held out longer.在那样情况下，我们本来可以坚持更久的。（实际上没有坚持很久）,八、may (not) have done 它表示“对过去可能会(不会)发生的事“ 的猜测。如 1、She may have missed the train.她也许误了车。 2、He may not have achieved all his aims But his effort is a good one.他可能没达到他的全部目的，但他还是认真做了努力的。 3、She may have gone to the clinic.她或许到医务宝去了。 4、“What has happened to Tom?“I dont know,. he may have got lost.“汤姆怎么了？“我不知道，他可能迷路了。“,九、m