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1、情态动词情态动词用法比较用法比较情态动词情态动词I.特点特点1）不能单独做谓语）不能单独做谓语 情态情态+do(be)(ought)to do(be)2)没有人称，数的变化没有人称，数的变化 He/We/They can swim.3）有的有时态变化）有的有时态变化can-couldmay-mightwill-wouldshall-shoulddare-daredneed-neededmustought to4)有的兼做实义动词有的兼做实义动词dare needII.用法比较用法比较1.can/could,be able toa)can 表示表示“会会”“能能”(ability)也可用也可用b
2、)be able to(强调自己的努力强调自己的努力,有多种时态有多种时态)c)eg.She can ride a bike.d)I think he will be able to pass e)the exam.f)He worked very hard but couldnt g)(wasnt able to)pass the exam.h)(否定句中无区别）否定句中无区别）Can/May/Could I use your telephone?Yes,you can/may.No,you cant/may not/mustnt.(Am.En)(Br.En)Can his son use
3、the car whenever he likes?Cant I stay up till the end of the program?d)can 的惯用语的惯用语1.can but/can only 作作“只好只好”“至多不过至多不过”讲讲,2.后接原形动词后接原形动词.前正式用语前正式用语.一般多用一般多用can only.3.We can but(can only)do our best.4.我们只好尽力而为我们只好尽力而为.5.I can but lose the money.6.我至多不过损失这笔钱我至多不过损失这笔钱.(不会更糟了不会更糟了)7.2.cannot(choose/h
4、elp)but/cannot help 8.“不得不不得不”,“不能避免不能避免”,“不禁不禁”讲讲.前接不定式前接不定式,9.后接后接“-ing”,或代词或代词.后较口语后较口语.I cannot(help)but admire your decision.She is a very selfish woman,but somehow you cant help liking her.3.cannot too“无论怎样无论怎样都不过分都不过分”,“越越越好越好”.We cant be too careful in the choice of our friends.I cannot than
5、k you too much.You cannot do it too well.3.must/have to/have got to(Am.E)a)肯定句中肯定句中 must“必须必须”“一定一定”。否定句中否定句中“不许不许”“禁止禁止”。have to“得得”，否定句，否定句“不必不必”。You must do as I told you to.You mustnt turn on the TV yourself.Cars must not be parked in front of the entrance.b)用用 must 提问，否定句答语提问，否定句答语 neednt Must
6、we do it now?Yes,you must.No,you neednt/dont have to.c)must 强调主观。表说话者的命令强调主观。表说话者的命令 或强烈的劝告。或强烈的劝告。have to/have got to 客观，时态变化多。客观，时态变化多。eg.You must be ready before 10.You have to be ready before 10.Thats an order.Need I type the letter today?Yes,you must.No,you neednt/dont have to.b)实义：有人称，时态，数的变化。
7、实义：有人称，时态，数的变化。注意区别情态用法。注意区别情态用法。You dont need to worry about the test.(dont have to)You neednt worry about the test.6.should/ought to前命令，前命令，劝告之意。后表因责任，劝告之意。后表因责任，义务而该做某事，语气较前重。义务而该做某事，语气较前重。We ought to obey the school rules.We should master a foreign language at least.7.will/woulda)助动词：前用于一般将来时，助动
8、词：前用于一般将来时，b)后用于过去将来时。后用于过去将来时。b)情态：表意愿，意志，情态：表意愿，意志，前用于一般时，后用于过去时。前用于一般时，后用于过去时。If you will take off your old clothes,well fit the new clothes on you.When we asked them if they wanted to go with us.They said they would.c)疑问句中用于第二人称，表询问对方疑问句中用于第二人称，表询问对方 意愿或向对方提出请求。意愿或向对方提出请求。would 比比will更客气。更客气。Wil
9、l you please pass me the newspaper?Wont you sit down?Would you like some tea?8.shall/shoulda)助动词：前用于一般将来时，助动词：前用于一般将来时，后用于过去将来时。后用于过去将来时。b)情态动词情态动词:用于二，三人称表说话人用于二，三人称表说话人 的意愿，表命令，警告，的意愿，表命令，警告，威胁，强制，允诺，决心。威胁，强制，允诺，决心。You shall have the book tomorrow.(允诺允诺)Nothing should prevent us from going for it.
10、(决心决心)c)疑问句用于一，三人称，疑问句用于一，三人称，征询对方意见或请求指示。征询对方意见或请求指示。Shall we go out for a walk?Shall I open the door for you?Shall he come here tomorrow?d)should 可用于表示推测。可用于表示推测。意为意为“理应理应”。Its nearly 7 oclock.Jack should be here at any moment.-He isnt here right now.-What time do you expect him?-He should be home
11、 around nine or so.She has been studying hard.She should do well on the test tomorrow.I think hes at home now;he should be taking a nap.He does it each afternoon.III.情态动词表示推测情态动词表示推测肯肯否否 疑问疑问非常肯定非常肯定猜测猜测cant do/be be doingmust do/be be doing Canmay/might do/be/be doingmay/might/couldnot do/be/be doi
12、ngmay肯肯否否 疑疑非常肯定非常肯定must have done/beencant/couldnthave done/beenCould猜测猜测might/may have done/been might/may not have done/been-There were already five people in the car but they managed to take me as well.-It couldnt have been a very comfortable journey.Jack cant have arrived yet,otherwise he would
13、 have telephoned me.IV.情态动词情态动词+have done/beena)表推测：表推测：-must have done/been-cant/couldnt have done/been-might/may have done/been-might/may not have done/been-could have done/been b)虚拟虚拟-should have done/been ought to have done/been（责备）（责备）-shouldnt have done/been ought not to have done/been（责备）（责备）
14、-need not have done/been （抱怨）（抱怨）-couldnt have done/been You shouldnt have opened the letter!It wasnt for you.You should(ought to)have answered the letter a week ago.Why didnt you?You were stupid to go skiing there-you could have broken your leg.You couldnt have missed the train if you had started t
15、en minutes earlier.Exercises:1.We havent got much time.We _ hurry.2.A.may B.can C.might D.must3.2.Weve got plenty of time.We _ hurry.4.A.mustnt B.neednt C.may not D.cant5.3.They havent lived here for very long.They 6._ many people.7.A.cant know B.mustnt know 8.C.shouldnt know D.neednt knowDBA6.-The
16、phone is ringing.Who do you think it is.-It _ Tom.A.should be B.might have been C.must have been D.could be7.-Jack always has difficulty getting up.-He _ to bed so late.A.shouldnt go B.neednt go C.shouldnt have gone D.neednt have gone 8.He _ wear a suit to work but he usually does.A.mustnt B.doesnt
17、have to C.doesnt D.shouldnt DAB9.Why did you stay at a hotel when you went to New York?You _ with Barbara.A.can stay B.could stay C.could have stayed D.might stay10.Im very hungry,I _ eat a horse.A.must B.can C.should D.could11.-Will you stay here for night?-Sorry,I _.My parents are waiting for me.A.cant B.neednt C.mustnt D.wontCDA12.-Joan is visiting her mother today.-In that case,_ you have dinner with us today?A.will B.wouldnt C.wont D.can 13.-Where were you yesterday afternoon?I tried to call you.-I _ to the library for a while.A.must go B.should go C.would go D.had to goCD