助动词和情态动词备用.ppt

,语法特征,1. 情态动词没有人称和数的变化,即情态动词第三人称单数不加- s (have to, have got to, be able to 除外)。,2. 情态动词本身具有一定词义, 但意思不够完整, 不能单独做谓语, 后接动词原形一起构成谓语部分 (ought to, have to/have got to, be able to除外)。 3. 情态动词无非谓语形式,即无不定式、分词等形式。,Sum up,1. can和be able to 1) can (could) 表示能力、可能, 只用于现在式和过去式 2) be able to可以用于各种时态。,只用be able to的情况： a. 位于助动词后。Has/have been able to b. 情态动词后。 We must/may be able to Show How Science is Beneficial to c. 用于句首表示条件。 Being able to get the tickets for that Hockey game, I am very excited now. 能买到那个冰球比赛的票，我现在非常激动。 d. 表示成功地做了某事时,只能用was/ were able to,不能用could。,注意:could还可不表示时态,只表示 1) 提出委婉的请求,回答中不可用could。 - Could I have the television on? - Yes, you can. / No, you cant. 2) 在否定、疑问句中表示推测或怀疑。 He couldnt be a bad man.,2. may和might 1) 表示允许或请求;表示没有把握的推测;may 放在句首,表示祝愿。 e.g. May God bless you! He might be at home. 注: might 表示推测时,不表示时态。只是可能性比may 小。,2) 成语:may/might as well,后面接不带to 的不定式，意为“不妨“。 e.g. If that is the case, we may as well try.,3. have to和must 1) 两词都是“必须”的意思, have to 表示客观的需要, must 表示说话人主观上的看法, 即主观上的必要。 e.g. My brother was very ill, so I had to call the doctor in the middle of the night. He said that they must work hard.,2) have to有人称、数、时态的变化,而must只有一种形式。但must可用于 间接引语中表示过去的必要或义务。 e.g. He had to look after his sister yesterday.,3) 在否定结构中：dont have to 表示“不必”; mustnt表示”禁止”。 e.g. You dont have to tell him about it. 你不必把这事告诉他。 You mustnt tell him about it. 你不能把这事告诉他。,4. must表示推测 1) must用在肯定句中表示较有把握的推测,意为“一定”。 2) must表对现在的状态或现在正发生的事情的推测时, 后面通常接系动词be的原形或行为动词的进行时。,e.g. You have worked hard all day. You must be tired.（对现在情况的推测判断) He must be working in his office. 他一定在办公室工作呢。 比较: He must be staying there. 他现在肯定呆在那儿。 He must stay there. 他必须呆在那儿。,表推测,不表推测,3) must 表示对已发生的事情的推测时, 要接完成时。 e.g. I didnt hear the phone. I must have been asleep. 4) must表示对过去某时正发生的事情的推测, 后面要接不定式的完成进行时。,e.g. -Why didnt you answer my phone call? -Well, I must have been sleeping, so I didnt hear it. 5) 否定推测用cant. e.g. If Tom didnt leave here until five oclock, he cant be home yet.,5.表示推测的用法 can, could, may, might, must 皆可表 示推测,其用法如下： 1) 情态动词+动词原形,表示对现在或将来的情况的推测,此时动词通常为系动词。 e.g. I dont know where she is. She may be in Wuhan.,2) 情态动词+动词进行时, 表示对现在或将来正在进行的情况进行推测。 e.g. At this moment, our teacher must be correcting our exam papers.,3) 情态动词+动词完成时, 表示对过去情况的推测。 e.g. The road is wet. It must have rained last night.,4) 情态动词+动词的完成进行时, 表示对过去正在发生事情的推测。 e.g. Your mother must have been looking for you.,5) 推测的否定形式,疑问形式用cant, couldnt表示。 e.g. Mike cant have found his car, for he came to work by bus this morning. 注: could, might表示推测时不表示时态,其推测的肯定程度不如can, may。,6.情态动词+have+过去分词 1) may (might) have + done sth., can (could) have + done sth. 表示过去,推测过去时间里可能发生的事情。,e.g. Philip may (might) have been hurt seriously in the car accident. Philip can (could) have been hurt seriously in the car accident.,2) must have+done sth., 表示对过去时间里可能发生的事情的推测,语气较强,具有“肯定”的意思。 e.g. - Linda has gone to work, but her bicycle is still here. - She must have gone by bus.,3) ought to have done sth./should have done sth.本应该做某事,而事实上并没有做; 否定句表示“不该做某事而做了”。,e.g. You ought to (should) have been more careful in this experiment. He ought not to have thrown the old clothes away.(事实上已扔了。) 注: ought to 在语气上比should 要强。,4) neednt have done sth. 本没必要做某事 e.g. I dressed very warmly for the trip, but I neednt have done so. The weather was hot. 5) would like to have done sth. 本打算做某事 e.g. I would like to have read the article, but I was very busy then.,7. should和ought to should 和ought to 都为“应该”的意思,可用于各种人称。 e.g. - Ought he to go? - Yes. I think he ought to. 表示要求,命令时,语气由 should(应 该)、(had better最好)、must(必须) 渐强。,8. had better表示“最好” had better 相当于一个助动词,它只有一种形式,它后面要跟动词原形。 had better (not) do sth.,e.g. It is pretty cold. Youd better put on my coat. Shed better not play with the dog. had better have done sth. 表示与事实相反的结果,意为“(过去)本来最好”。 e.g. You had better have come earlier.,9. would rather表示“宁愿” would rather (not) do would ratherthan宁愿而不愿 would sooner had rather had sooner表示“宁愿“、“宁可“的意思。 e.g. If I have a choice, I had sooner not continue my studies at this school.,10. will和would 1) would like to do = want to 想要 e.g. Would you like to go with me? 2) Will you? / Would you like? 表示肯定含义的请求劝说时,疑问句中一般用some, 而不是any。 e.g. Would you like some cake?,3) 否定结构中用will, 一般不用would, wont you是一种委婉语气。 e.g. Wont you sit down?,11. need和dare 这两词既可做实义动词用,又可做情态动词用。作为情态动词,两者都常用于疑问句,否定句和条件句。并注意回答用need 提问的句子时，肯定回答用must。 need 作实义动词时后面的不定式必须带to,而dare作实义动词用时, 后面的to时常可以被省略。,1) 实义动词: need+ n. / to do sth. 2) 情态动词: need,只用原形need后加do,否定形式为need not. e.g. - Need you go yet? - Yes, I must. / No, I neednt. 3) need, want, require, worth(形容词)后面接doing也可以表示被动。 need doing = need to be done,I cant find my purse anywhere. You _ have lost it while shopping. A. may B. can C. should D. would,A,2. Although this _ sound like a simple task, great care is needed. A. must B. may C. shall D. should 3. You _ be hungry already you had lunch only two hours ago! A. wouldnt B. cant C. mustnt D. neednt,B,B,4. Im sorry. I _ at you the other day. Forget it. I was a bit out of control myself. A. shouldnt shout B. shouldnt have shouted C. mustnt shout D. mustnt have shouted,B,5. According to the air traffic rules, you _ switch off your mobile phone before boarding. A. may B. can C. would D. should 6. When I was young, I was told that I _ play with matches. A. wouldnt B. neednt C. mustnt D. darent,D,C,7. It is usually warm in my hometown in March, but it _ be rather cold sometimes. A. must B. can C. should D. would 8. You dont have to know the name of the author to find a book. You _ find the book by the title. A. must B. need C. can D. would,B,C,9. What sort of house do you want to have? Something big? Well, it _ be big thats not important. A. mustnt B. neednt C. cant D. wont 10. She _ have left school, for her bike is still here. A. cant B. wouldnt C. shouldnt D. neednt,B,A,Exercises,1. A left-luggage office is a place where bags _be left for a short time, especially at a railway station. A. should B. can C. must D. will,B,2. How _ you say that you really understand the whole story if you have covered only part of the article? A. can B. must C. need D. may,A,3. The room is so dirty. _we clean it? Of course. A. Will B. Shall C. Would D. Do 4. My English-Chinese dictionary has disappeared. Who _ have taken it? A. should B. must C. could D. would,B,C,5. Is John coming by train? He should, but he _ not. He likes driving his car. A. must B. can C. need D. may,D,6. I heard they went skiing in the mountains last winter. It _ true because there was little snow there. A. may not be B. wont be C. couldnt be D. mustnt be,C,7. It has been announced that candidates _ remain in their seats until all the paper have been collected. A. can B. will C. may D. shall 8. I hear youve got a set of valuable Australian coins. _ I have a look? Yes, certainly. A. Do B. May C. Shall D. Should,D,B,9. Oh, Im not feeling well in the stomach, I _ so much fried chicken just now. A. shouldnt eat B. mustnt have eaten C. shouldnt have eaten D. mustnt eat,C,10. I was really anxious about you. You _ home without a word. A. mustnt leave B. shouldnt have left C. couldnt have left D. neednt leave,B,11. You cant imagine that a well-behaved gentlemen _ be so rude to a lady. A. might B. need C. should D. would 12. Write to me when you get home. _. A. I must B. I should C. I will D. I can,C,C,13. Mr. Bush is on time for everything. How _it be that he was late for the opening ceremony? A. can B. should C. may D. must,A,14. Are you coming to Jeffs party? Im not sure. I _ go to the concert instead. A. must B. would C. should D. might,D,15. My sister met him at the Grand Theatre yesterday afternoon, so he _ your lecture. A. couldnt have attended B. neednt have attended C. mustnt have attended D. shouldnt have attended,A,16. Sorry, Im late. I _ have turned off the alarm clock and gone back to sleep again. A. might B. should C. can D. will,A,17. There was a lot of fun at yesterdays party. You _ come, but why didnt you? A. must have B. should C. need have D. ought to have,D,18. 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,19. I stayed at a hotel while in New York. Oh, did you? You _with Barbara. A. could have stayed B. could stay C. would stay D. must have stayed,A,20. The fire spread through the hotel very quickly but everyone _ get out. A. had to B. would C. was able to D. could,C,21. Jack _ yet, otherwise he would have telephoned me. A. mustnt have arrived B. shouldnt have arrived C. cant have arrived D. neednt have arrived,C,22.When he was there, he _ go to that coffee shop at the