专四情态动词讲解课件.ppt

情态动词情态动词*情态动词情态动词:will（愿意）,shall（将）,must（必须）,can,may,would,should(应该),might,could,ought to,used to（过去常常）,need（需要）,dare（竟敢），have to（不得不）1.表示已经发生的情况表示已经发生的情况(1)must have+过去分词，表示对已发生情况的肯定推测，译为“(昨 天)一定”。如：My pain must have been apparent the moment I walked into the room,for the first man I met asked sympathetically:“Are you feeling all right?”(2)cant/couldnt have+过去分词，表示对已发生情况的否定推测，译为“(昨天)一定没”。如：Mary couldn t have received my letter;otherwise she would have replied before now(3)may/might have+过去分词，表示对已发生的事情做不肯定、可能性很小的推测，或事实上根本没发生，译为“也许”。如：At Florida Powers Crystal River plant,a potentially serious leakage of radioactive water may have been unknowingly caused by an electrician.2.表示虚拟语气表示虚拟语气(1)neednt have+过去分词，表示做了不必做的事，译为“其实没必要”。如：As it turned out to be a small house party,we neednt have dressed up so formally.注意：did not need to do 动作并没发生 例：I didnt need to get up early,so I got up until 9 a.m.(2)should/should not have+过去分词，表示应该做某事但实际上未做，或本不应该做但实际上做了,译为“本(不)应该”。如：I regret having left the work unfinished;I should have planned everything ahead carefully.(3)ought to have+过去分词，表示动作按理该发生了，但实际上未发生，译为“该”，与should的完成式含义类似。如：The porter ought to have called t he fire-brigade as soon as he saw the fire in the stock,which went up in smoke.(4)could have+过去分词，表示过去本来可以做但却未做，译为“完全可以”。如：What you said is right,but you could have phrased it more tactfully.(5)may/might have+过去分词，表示过去可以做但实际未做，译为“(那样)也许会”。如：It might have been better to include more punchy statistics and photos of equipment in the introduction to further assist first-time office automation managers.3.几个情态动词常考的句型几个情态动词常考的句型(1)may/might(just)as well“不妨，最好”，与had better相近。如：Since the flight was cancelled,you might as well go by train.(2)cannot/canttoo“越越好，怎么也不过分”。注意这个句型的变体cannotover。如：You cannot be too careful when you drive a car.The final chapter covers organizational change and development.This subject cannot be overemphasized.(3)usednt或didnt use to为used to(do)的否定式。(4)should 除了“应该”一层意思外，大纲还规定要掌握其“竟然”的意思。如：I didnt expect that he should have behaved like that 情态动词一般用法的否定：情态动词一般用法的否定：mustnt 不准,禁止，不要 cant(couldnt)不会；不能；may(might)not 不可以;neednt 没必要(=dont have to)used notusednt to或didnt use to 过去不dare not 不敢*情态动词情态动词have过去分词结构表示轻微的责备和后悔过去分词结构表示轻微的责备和后悔 肯定：过去应该做而没有做；否定：过去不该（不必）做而做了。mightcouldhave过去分词：“本来可以，早就应该”（只用于肯定句，且不能用（只用于肯定句，且不能用may,can）You could have told me you were going to be late!.你应当早告诉我你会晚到的！should（ought to）have过去分词：“本应”（没做）should not（ought not to）have过去分词：“本不该”（做了）You should not have handed in your composition yesterday morning.你本不应把作文交了。You should have been here earlier.你应该早点来才对。.3.neednthave过去分词：“本不必，本不须”（need只用于否定句）（做了）You neednt have woken her up.Its only six你其实不必叫醒她。现在才六点。注意：注意：did not need to do 动作并没发生动作并没发生（没做）（没做）例：I didnt need to get up early,so I got up until 9 a.m 八大注意点八大注意点1.在以could,might 表示征询对方意见或表示请求时，回答应相应使用can,may Might I watch TV after supper?Yes,you _.A.may B.must C.might D.can2.May I/we？这一类疑问句的肯定回答为Yes,please.或Certainly；否定回答为Please dont.或No,you mustnt.例如：“May we leave now?”“No,you mustnt.You havent finished your home work yet.”3.need I/we？这一类疑问句的肯定回答为Yes,we must;否定回答为neednt 4.在回答must引起的问题时，肯定must;如果是否定的答复，不能用mustnt，而要用neednt或dont have to5.I wish to go home with you,may I?6.Do help yourself to have fruit,wont you/will you?（表示一种委婉的请求）7.Shall 用于第三人称，表示许可，允许8.lets do this job,shall we?Let us do this job,will you?9.should 也表示惊讶的语气，例如：I was shocked that she should have said such a thing to you.(她竟然对你说那样的话,)两大类区别：两大类区别：一、表示能力:can,be able to be able to 能用于各种时态。can/could 只能表示现在或过去的能力*was/were able to:“设法做成某事”相当于相当于 managed to do sth succeeded in doing sth.be able to与 can1）cancould 表示能力；可能(过去时用could),只用于现在式和过去式(could)。be able to可以用于各种时态。They will be able to tell you the news soon.他很快就能告诉你消息了。2）只用be able to a.位于助动词后。b.情态动词后。c.表示过去某时刻动作时。d.用于句首表示条件。e.表示成功地做了某事时，只能用was/were able to，不能用could。He was able to flee Europe before the war broke out.=He managed to flee Europe before the war broke out.can用于表示“能力”时是指现在的能力，过去或将来的能力通常用was/were able to或will/shall be able to表示。eg.She was able to go to school yesterday.Soon she will be able to swim a quarter of a mile.Can的过去式形式could也可用于表示泛指过去的能力。如：I could read when I was four.但不能用于表示特定的某一过去能力，如不能说：*He could swim halfway before he got tired.He was able to swim halfway before he got tired.上述这种用法的区别不存在于否定句中。在否定句中，couldnt与was/were not able to 可以互换使用。eg.I couldnt see him again before he left.I wasnt able to see him again before he left.注意的一点是：can也可以用于表示“许可”。它可以表示现在许可或将来许可，过去许可用could表示，此时一律不能用be able to的某种形式替换。二、used to 和would 的区别used to过去常常（但现在已无此习惯现在已无此习惯，would无此含义）He used to drink beer,now he drinks wine.他过去喝啤酒，现在喝白酒。would只能用来谈动作；只能用来谈动作；used to用来谈动作或状态（可用来谈动作或状态（可与与be,live,like,stay等状态动词连用）：等状态动词连用）：He would get up early when he lived in the country.他住在乡下时总是早起。We used to live in a small town.（不能用would）Be used to doing sth:习惯于做某事习惯于做某事 should的用法的用法 1.(shall的过去式的过去式,表示过去将来表示过去将来)将将We hoped that we should be able to do that.我们希望我们能这样做。我们希望我们能这样做。2.(表示语气较强的假设表示语气较强的假设)万一万一,竟然竟然If the car should break down on the way,you would have to walk back.万一汽车中途抛锚万一汽车中途抛锚,你就得走回来。你就得走回来。3.(表示可能性、推测、推论或期待表示可能性、推测、推论或期待)可能可能,该该She should be here any minute.她该马上就到。她该马上就到。Dinner should be ready by now.此刻晚饭应该做好了。此刻晚饭应该做好了。4.(表示义务、责任表示义务、责任)应该应该,应当应当You should do as she says.你应当照她说的去做。你应当照她说的去做。He should work harder.他应该更加努力。他应该更加努力。You should help your mother with the housework.你应该帮你母亲做家务。你应该帮你母亲做家务。5.(表示委婉、谦逊表示委婉、谦逊)可可,倒倒6.(表示感情、意志等表示感情、意志等)竟然会竟然会;应该应该Im sorry it should be this way.很遗憾很遗憾,事情竟会是这个样子。事情竟会是这个样子。Its strange that he should be absent.真奇怪，他竟会缺席。真奇怪，他竟会缺席。You shouldnt have told him about it.你不该把这件事告诉他的。你不该把这件事告诉他的。7.(表示建议、命令、决定等表示建议、命令、决定等)应该应该,必须必须Crime should be punished.犯罪应受惩罚。犯罪应受惩罚。8.(表示目的表示目的)会会,可以可以He stood away so that we should enter the room first.他让开一步他让开一步,让我们先进屋。让我们先进屋。9.(表示结果、意愿等表示结果、意愿等)就就,该该10.(表示征求同意等表示征求同意等)可以可以,该该Who should I see about my schedule 1.You _ Jim anything about it.It was none 1.You _ Jim anything about it.It was none of his business.of his business.（20042004）A.neednA.neednt have told B.neednt have told B.neednt tell t tell C.mustnC.mustnt have told D.mustnt have told D.mustnt tellt tellA，neednt have done表示本不必做而做了。没有mustnt have done的形式，但可以说cant have done，表示不大可能。2.He _ the 8:20 bus because he didn2.He _ the 8:20 bus because he didnt t leave home till 8:25.leave home till 8:25.（19941994）A.couldnA.couldnt have caught B.ought to have t have caught B.ought to have caughtcaught C.shouldn C.shouldnt have caught D.must not have t have caught D.must not have caughtcaughtA，couldnt have done表示不可能做了某事3.He _ unwisely3.He _ unwisely，but he was at least but he was at least trying to do something helpful.trying to do something helpful.（19991999）A.may have acted B.must have acted A.may have acted B.must have acted C.should act D.would actC.should act D.would actA.may have done表示过去可能做过某事，表示过去可能做过某事，B表表示一定做过，推测的可能性很大示一定做过，推测的可能性很大4.Loudspeakers were fixed in the hall so that everyone _an opportunity to hear the speech.（06）A.ought to have B.must have C.may have D.should haveD.So that 引导的目的状语从句，与情态动词的搭配有：so that+主语+may,might,shall,should等。因为主语用过去时，所以D选项符合题意6.“You _borrow my notes provided you take care of them,”I told my friend.(07)A.could B.should C.must D.canD.Provided(that)+从句表示一种假设条件，provided 相当于if。根据情况可使用虚拟语气或陈述语气，这里表示真实的条件句。英语中表示”许可，建议“，在口语中常用can/may,而不用could/might.这里正是口语中的给与”许可“的意思。故D正确。7.She_fifty or so when I first met her at the conference.（07）A.must be B.had been C.could be D.must have beenD.英语中表示”肯定“的推测，用情态动词must。如果是对现在的推测，用must do;对过去的推测，是must have done.这里是对过去的推测，故D正确。8.Which of the following sentence expresses“probability”?（08）A.You must leave immediatelyB.You must be feeling rather tiredC.You must be here by eight oclockD.You must complete the reading assignment on time B.Must 作为情态动词以用来表命令，必须如何；二表示肯定推测，可能会怎么。A意为”你必须马上离开.C意为”你必须8点前到这儿“D.意为你必须按时完成阅读作业“。这三句中must都是第一种用法。B意为”你肯定感觉到累了“这是第二种用法，肯定的判断，表示可能性，故为答案。9.I went there in 1984,and that was the only occasion when I _the journey in exactly two days.(05)A.must make B.must have madeC.was able to make D.could makeC.Can 表示一般性的能力，而be able to可特指某一次”能够“10.Nancys gone to work but her cars still there.She_ by bus.A.must have gone B.should have gone C.ought to have gone D.could have gone A.Must 在肯定句中表示较有把握的推测，意为”一定“，当must后接完成时的时候，表示对过去事情的肯定推测。Should have done/ought to have done 均表示本应该做而没做,could have done 表示”本可以做而没有做“，均排除，据题意。A正确。