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1、,The Usage of the Modal Verbs,情态动词,情态动词,表示推测,不表示推测,can could may might shall should must will would ought to,have to dare (darent) need (neednt) used to,The feature（特点） of the modal verbs: 1. 情态动词本身有词义, 但词义不完全. 2. 不能单独作谓语,只能和动词原形一起构成谓语. 3. 情态动词没有人称和数的变化( 除“have to”外). 4. 没有不定式、-ing 分词、-ed 分词形式.,1) H
2、e can/could/must/may/might/shall/ should/need/dare/will/would/ought to/ + work in that factory.,2) He has to go home now.,3) He had to look after his sick mother.,4) I will have to go home because my mother is ill.,must与 have to用法对比,must have to,1.表“必须”,(主观看法)必须; 没有过去式,可用于间接引语中. He told me I must do
3、 according to what he said.,(客观需要)不得不;(有多种时态.) -Its raining heavily, so we cant go now. -I think well have to wait till the rain stops.,2.疑问句及答语中,Must I ? Yes, you must.(一定) No, you neednt. No, you dont have to,Do you have to go today? Yes, we do. 否定句: You dont have to worry about that.,Have to 用于反意
4、问句,You wont have to worry about rank or spy, will you?,He had to wait for the next bus, didnt he?,Her mother is ill. She has to leave here, doesnt she?,3. 带must句子的反意问句,He must do it all over again, mustnt he?,(必须),We must finish the work in an hour, neednt we?,(必要),You mustnt walk on grass, must you
5、?,(禁止),Your head teacher must be in his office.,He must be cleaning the room.,I didnt hear the phone. I must have asleep.,must 表肯定推测:,You must be hungry now, _?,= Im sure you are hungry now.,He must be watching TV now, _?,= Im sure he is watching TV now.,Tom must have lived here for a long time, _?,
6、= Im sure Tom has lived here for a long time.,She must have arrived yesterday, _?,= Im sure she arrived yesterday.,*陈述部分的must表示“一定”,“想必”等推测意义时,要根据陈述部分的不定式结构, 在附加疑问部分采用与其相适应的主动词或助动词形式.,arent you,isnt he,hasnt he,didnt she,should与ought to用法对比,should ought to,1.表“应当”,表示劝告,建议,You should listen to the do
7、ctors advice.,We should learn from Zhang Hua.,表示“有义务或有必要”做某事,You ought to finish your work before you go home.,We ought to help each other.,2.表可能的猜测,They should get home by now.,表非常可能的事“总应该”,If we start to work right now, we ought to finish it before lunch.,2. Ought to 疑问式及否定式,Ought he to go? Yes, I
8、 think he ought (to).,He ought not to leave the work tomorrow. (oughtnt to leave),(不能说ought to not do),3.表 对于现在的状况不满. (应做的事 没做),Should Ought to,+ be + doing,Should not ought not to,+ be + doing,You shouldnt be watching TV. You should be doing your homework. You oughtnt to be playing basketball. You
9、ought to be having lunch.,3.表对过去的动作的 “责备” 或 “惋惜”,Should Ought to,+ have +P.P.该做，而没有做,Should not ought not to,+ have + P.P. 不该做，而做了,The plant is dead. I ought to have given it more water.,You should not have left your baby alone in the house.,can could,1.表“能力”,Can you lift this heavy box?,I couldnt u
10、nderstand what he said at all.,2.表“许可”,You can use a different material instead.,He said I could borrow his bike.,3.表“怀疑” “可能性”,No, no, it cant be true. What on earth can this mean?,can与could用法对比,We thought the story couldnt be true. / How could you be so careless?,4.表 “猜 测”,a.can用于疑问句中: 否定答案用cant;
11、肯定答案用must.,Can he be in the library? He cant be in the library. He must be at home.,b.can+have+P.P.表示对过去的推测 (限于问句中).,Can he have said so? 他可能这样说吗?,c.cant+have+P.P.表 示对过去的否定推测,She cant have said such a foolish thing. 她不可能说这样愚蠢的事.,d. could+have+P.P: 表示本来能做得到, 但事实上未做到.,He could have finished the task o
12、n time, but the heavy snow came.,e.couldnt+have+P.P表示对过去某事的否定性猜测,He couldnt have been to that town.,注:,could代替can,表示语气较为婉转.,Could I use your bike?,You could do it this way.,can(能够)=be able to(仅表示能力时),但 be able to 表示经过一番努力后,才能做得到.且有更多的时态.,He was a good swimmer, so he _ swim to the river bank when the
13、 boat sank. A. could B. might C. shall D. was able to,D. was able to,may与might用法对比:,may might,1.表“询问”,May I ? (=Can I ?),Might I ? (=Could I ?) (但比用may更客气.),2.表“许可”,You may take the boy there,He told me he might come.(might与told 相呼应.),3.表“可能” “或许”,She may not like this place.,Im afraid he might not
14、like this place.,4.表“猜测”,a. may(might)+V.表示对现在事情的猜测.(might比 may可能性更小一些.),Now he might know her address.,Be careful, you might break the glass.,b. may(might)+ have+P.P,表示对过去事情的猜测, 认为某事“可能”发生.(might比may更含蓄,或更不肯定.),He may (might)have played electric game on TV the whole night.(For he looks very sleepy.
15、),注:,may I ? 的答语.,肯定: Yes, you can. 否定: No, you mustnt (语气强硬) No, you may not.或 No, youd better not.,may(might)用于目的状语从句中.,The emperor gave them some gold in order that they might begin their work at once.,注:,may用于祈使句中表示祝愿,May you succeed! May you have good luck!,3. shall,1) 作助动词，用于第一人称，表示将来，should 是shall 的过去式 We shall start for Beijing tomorrow.,2) 作情态动词， A: 用于第一人称，表示征求对方意见或请求 Shall we begin our lesson? Shall I sit here?,
