第八讲 情态动词

1、高中英语：情态动词一、情态动词的概述情态动词表示说话人的语气和情态，如需要、可能、意愿和怀疑等，有一定的意义但是不完整，必须和动词原形一起构成谓语。常见的情态动词有：can, could, may, might, must, ought to, need, dare, shall, will, should, would, be able to.二、情态动词的具体用法1. can （其过去式为could）1) 表示能力，意为“能够” She can speak English.Ø 比较：be able to 强调设法做成了某事 =manage to do The fire was v

2、ery big, but most people were able to escape from it. 表示将来的能力时，一般要用be able toThe baby will be able to walk in a few days.2) 用于肯定句中，表示理论上的可能性。Anyone can make mistakes.Dont throw it away and it can be useful in future.3) 用于否定句、疑问句中表示推测、怀疑、惊讶等,表示对过去的推测时，用can/could have done的结构。This cant be done by him.

3、Can it be true?How can you be so careless!4) 表示请求或许可，此时could比can语气更加委婉。-Could I come here again tomorrow?-Yes, you can. (回答时改用can)【练习】（1） A computer _ think for itself; it must be told what to do. A. cant B. couldnt C. may not D. might not （2）The fire spread through the hotel very quickly but everyo

4、ne _ get out.A. had to B. would C. could D. was able to（3） They will _ run this machine on their own in three months.A. can B. could C. may D. be able to(4) That big cinema _ seat 2,000 people.A. can B. should C. ought to D. is able to2.may & might 1) 表示可能性。 He said that he might not be free tha

5、t afternoon.He may/might be ill today.2) 表示许可，意为“可以”，此时在疑问句中might比may的语气更加委婉。You may go now.May/Might I use your pen? (否定回答用mustnt)3) may用于祈使句，构成“May+主语+动词原形”表示祝愿。May you be happy.May you succeed.4) may/might as well + 动词原形 意为“最好.，还是.好”We may as well stay here.5) may well do “大概会，可能会”You may well ge

6、t confused.6) may/might have done 表示对过去所发生的事情的推测。He may have said so.【练习】(1) Could I borrow your dictionary? Yes, of course you _. A. might B. will C. can D. should(2) Might I watch TV after supper? Yes, you _. A. may B. must C. might D. can3. must 1) 表示“必须”，强调主观看法（have to强调客观上必须）You must do everyth

7、ing as I do.表示“不必，没必要”时，用neednt 或 dont have to.You neednt go there at once.Ø 注意-Must we turn in our plan this week?-Yes, you must./No, you neednt/dont have to.2) （只用于肯定句中）表示肯定的推测。对目前状况的推测用 must do 或 must be doing，对过去的推测用 must have done.It must be raining outside.The light is on, so he must be a

8、t home.Look at his new car. He must have earned a lot of money.3) mustnt 意为“禁止”Children must not play with fire.4) 表示“偏要、非要、偏偏”Why must it rain on Sunday?Why must you do it?【练习】(1) You _ return the book now. You can keep it till next week if you like. A. cant B. mustnt C. neednt D. may not(2) Johnny

9、, you _ play with the knife, you _ hurt yourself. A. wont ; cant B. mustnt ; may C. shouldnt ; must D. cant ; shouldnt (3) -Will you stay for lunch? -Sorry, _. My brother is coming to see me. A. I mustnt B. I cant C. I neednt D. I wont(4) -May I pick a flower in the garden? - _.A. No, you neednt B.

10、Not, please. C. No, you mustnt D. No, you wont4. need “需要”1) need做名词时，构成There is no need (for sb) to do sth. 某人没有必要做某事。There is no need for us to tell her the news.2) sb need to do sth 某人需要做某事sth need to be done = sth need doing 某事物需要被做 （want, require）We need to buy some books.The flowers need to be

11、 watered.=The flowers need watering.Ø 注意对need问句的回答: -Need I finish the work today? -Yes, _. No, _. No, _.Ø neednt 对其它情态动词的回答: -Shall I tell John about it? -No, you _. -Must we do it now? -No, you _.5. dare “敢”1) 用作情态动词时，没有人称和数的变化，其后跟动词原形。2) 用作实意动词时，有人称和数的变化，其后跟to do.【练习】一、判断正误How dare you

12、say such a thing?How dare you to say such a thing?He darent to speak English before such a crowd, did he?He darent speak English before such a crowd, dare he?二、完成句子（1）She dare not go out alone.否定句：一般疑问句：过去时态的肯定句：过去时态的否定句：（2）She dares to go out alone.否定句：一般疑问句：过去时态的肯定句：过去时态的否定句：6. will1) 表示意愿、意图和决心，意

13、为“要、愿”(would是其过去式)Will we buy a car?I will do my best to help you.2) 疑问句中，与第二人称连用，表示“邀请、请求”(此时would比will更加委婉)Will you please turn down the TV?3) 表示对现在或将来的推测、估计，意为“可能，想必 “This will be the book you are looking for.That will be an insect.4) 表示经常性、习惯性、倾向性等，意为“经常，总是，大概，惯于”Oil will float on the water.The

14、man is strange. He will sit there for hours without saying anything.5) 用于祈使句的附加疑问句中Come here early tomorrow, will you?Dont go now, will you?【拓展】Let us go out for a walk, will you? (动作不包括主语you) Lets go out for a walk, shall we? (动作包括主语you)7. would1) 表示推测，意为“大概，也许“，可指现在或过去That would be in the spring o

15、f 1997.2) 表示过去的习惯，意为“过去常常做某事“The old man would sit near the fire for hours on winter evenings.3) 其他固定句型would like sth/to do sthwould rather do sth “但愿，宁愿做某事“would rather that从句 (要使用虚拟语气，时态向后倒)【练习】汉译英（1）我宁愿在这儿再待一周。（2）我宁愿你明天来。（3）我宁愿他上周就离开了。8. shall1) 用于一、三人称的疑问句中，表示征求对方的意见或向对方请示(should是其过去式，多用于间接引语中)S

16、hall she go now ?When shall we start the meeting?Mr. Lin asked if he should get his visa the next day.2) 用于二、三人称的陈述句中，表示说话人给对方的命令、警告、允诺或威胁You shall be punished if you do it again.You shall have the book when I finish reading it.3) 用于第一人称表决心We shall finish the task before Friday.We shall catch up wit

17、h them.4) 用于三人称，在条约、规定、法令文件中表示义务或规定，意为“必须，应该“No reader shall remove a book from the library without the permission of the librarian.【练习】（1） He _ be punished if he disobeys. 如果他不服从, 就要受到惩罚.（2） We are not going to quarrel at all if you _only let me speak. 只要你让我说话, 我们根本就不会吵架.（3） -Sir, _ he go or stay?

18、-Let him go. A. will B. shall C. might D. could （4） The door _ open. 这门经常打不开.(5) Ronald _ stay in his small garden for a long time every day in the past. A. could B. might C. should D. would(6) You _ have the book after I read it. 我看完以后一定把这本书给你9. should1) 表示责任、义务，意为“应当，应该“We should respect our teach

19、ers and parents.2) 表示按照常理经验进行的推测，意为“一定会、应该会“He should be sixty years old.He should have got there by now.3) 表示惊讶，难以置信或不应该发生的事情，意为“竟然“Why should he tell a lie?The man should be so rude to a lady.三、归纳总结1. 表示推测情态动词的重要用法. 情态动词对将来对现在对过去肯定的推测must/should+ V.常见must be+ V.+ be doing+ have done可能的推测may, might

20、+ V.+ V.+ be doing+ have done否定的推测cant, couldnt+V.+V.+ be doing+ have done疑问的推测can, could+ V.+V.+ be doing+ have done【过手训练】1. I don't know where she is, she _ be in Wuhan.2. At this moment, our teacher _ our exam papers. 这时，我们老师想必在批改试卷。 3. The road is wet. It _ last night. (rain)4. Your mother _

21、 for you.你妈妈一定一直在找你。 5. Philip _ seriously in the car accident. 菲利普可能在车祸中受了重伤.6. -Linda has gone to work, but her bicycle is still here. -She _ (go) by bus.7. Mike _ his car, for he came to work by bus this morning.迈克一定还没有找回他的车，因为早上他是坐公共汽车来上班的。 【高考选粹】1. I thought you _like something to read, so I ha

22、ve brought you some books. A. may B. might C. would D. must 2. Where is my pen? I _it. A. might lose B. would have lost C. should have lost D. must have lost3. I didnt hear the phone. I _asleep A. must be B. must have been C. should be D. should have been 4. -There were already five people in the ca

23、r, but they managed to take me as well. -It _a comfortable journey A. cant be B. shouldnt be C. mustnt have been D. couldnt have been 5. Its nearly seven oclock . Jack _be here at any moment. A. must B. need C. should D. could2. “情态动词 + have done”用法一览情态动词 + have done用法must have done对过去的肯定推测“想必。准是、一定是”否定式为：cant/couldnt have donecan/could have done1.过去可能会做2.本能够做某事却没有做can/could not have done1.过去不可能做2.过去本不可能做某事却做了may/might have done1.过去可能已经做了.2.might have done 过去可能会发生但未发生should/ought to have done本该做而没有做should not/ought not to have done本不该做而做了neednt have done本