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上一页首 页下一页1第1页上一页首 页下一页1)表示必定猜测时,各情态动词语气强弱以下:最强must(一定)will(很有可能)would(很有可能)ought to(应该,很有可能)should(应该,很有可能)can(可能)could(可能)may(可能)最弱might(可能)2)表示否定猜测时cant/couldnt语气最强,指“不可能”;may/might not语气最弱,意思是“可能不”。3)一些情态动词表猜测时使用方法限制。must只用于必定句;may/might普通不用于疑问句;could可用于各种句式;而can多用于否定句、疑问句,用于必定句时,多指“客观可能性”。如:Lightning can be very dangerous.闪电可能会非常危险。2第2页上一页首 页下一页情态动词情态动词 can,could,may,might,must表推测使用方法:表推测使用方法:情态动词中情态动词中can,could,may,might,must都表推测。其中都表推测。其中must可能性最大,可能性最大,can/could次之,次之,may/might最小。详最小。详细使用方法以下:细使用方法以下:1.must使用方法使用方法(1)表示推测)表示推测“可能性可能性”时,意思是时,意思是“一定、准是一定、准是”,语气较必定,较有把握。语气较必定,较有把握。He must be American.=It is certain that he is American.他准是个美国人。他准是个美国人。3第3页上一页首 页下一页(2)must表推测只能用于必定句。表推测只能用于必定句。如表示如表示“一定不、必定不一定不、必定不”意思时,应用意思时,应用cant,如问询某种可能时,应用如问询某种可能时,应用can。He must know my address.他必定知道我地址。他必定知道我地址。(一定)(一定)He cant know my address.他必定不知道我地址。他必定不知道我地址。(一定不)(一定不)Can he know my address?他知道我地址吗?他知道我地址吗?(问询可能性)(问询可能性)4第4页上一页首 页下一页(3)must表示推测时,能够推测现在表示推测时,能够推测现在/正在发生动作正在发生动作/过过去发生动作。去发生动作。He must have a car now.(现在)他一定有辆小汽车。(现在)他一定有辆小汽车。He must be doing his exercises in the classroom.(正在进行)他一定在教室里做练习。(正在进行)他一定在教室里做练习。He must have finished the work.(过去发生)他一定(过去发生)他一定已完成了工作。已完成了工作。注:注:must表示推测时表示推测时极少用于未来情况极少用于未来情况。普通不用。普通不用He must come tomorrow.可用可用Its certain/Im sure that he will come tomorrow.5第5页上一页首 页下一页(4)在反意疑问句中,当从属部分含有表示推测意义)在反意疑问句中,当从属部分含有表示推测意义must时,疑问部分助动词应与时,疑问部分助动词应与must后面动词在非推测情后面动词在非推测情况下使用方法保持一致。况下使用方法保持一致。He must be a worker,isnt he?(现在)他按时个工人,(现在)他按时个工人,是吗?是吗?You must have learned English for many years,havent you?(完成时)你一定学了好多年英语,是吗(完成时)你一定学了好多年英语,是吗?比较:比较:It must have rained last night,didnt it?(过去)昨晚(过去)昨晚一定下雨了,是不是?一定下雨了,是不是?He must have arrived by yesterday morning,hadnt he?6第6页上一页首 页下一页2.can/could使用方法使用方法(1)can表示推测表示推测“可能性可能性”时,往往用于否定句或疑时,往往用于否定句或疑问句。问句。Cant“一定不一定不”,can在疑问句中意思是在疑问句中意思是“会、可会、可能能”。He cant be at home.=It is impossible that he is at home.他一定不在家。他一定不在家。(2)can/cant+have done,表示对过去发生动作进,表示对过去发生动作进行推测。行推测。He cant have gone to Shanghai for I saw him a minute ago.他不可能去了上海,我刚才还看见他。他不可能去了上海,我刚才还看见他。Its so late.Where can she have gone?天晚了,她可天晚了,她可能去哪儿了呢?能去哪儿了呢?7第7页上一页首 页下一页(3)could 还能够用于表示客气、委婉、礼貌请还能够用于表示客气、委婉、礼貌请求语气。求语气。Excuse me,could you tell me the way to the bus station?Could you help me?(4)could have done 本能做但未做,表虚拟语气本能做但未做,表虚拟语气 I could have done it well,but I wasnt so careful then.8第8页上一页首 页下一页3.may和和might使用方法使用方法(1)may,might表示推测表示推测“可能性可能性”时,意思是时,意思是“可能可能”、“可能可能”He may/might be American.=It is possible that he is American.他可能是个美国人。他可能是个美国人。注:注:might不表示过去时态,只是语气上比不表示过去时态,只是语气上比may更委婉,更委婉,表示可能性更小。表示可能性更小。(2)may,might表推测时,能够用于否定句,意思是表推测时,能够用于否定句,意思是“可能不、可能不可能不、可能不”,但,但不用于疑问句不用于疑问句。He may/might not be at home.他可能不在家。他可能不在家。9第9页上一页首 页下一页(3)may,might能够推测现在正在发生动作或过去发生能够推测现在正在发生动作或过去发生动作。动作。He may/might be sleeping now.The boy may/might not be watching TV at home.这个男孩可能没在家看电视这个男孩可能没在家看电视These students may/might have seen the film before.(过去)(过去)这些学生以前可能看过这部电影。这些学生以前可能看过这部电影。10第10页上一页首 页下一页1.That man must be Sarahs husband.-No,he_ be her husband.She is still single.A.cant B.mustnt C.may not D.ought to2.Peter _come with us tonight,but he isnt very sure.A.must B.may C.can D.will11第11页上一页首 页下一页 3.What_ it be?-It_ be a mail box,for it is moving.It_ be a car.A.can;cant;must B.can;can;mustC.can;mustnt;must D.must;mustnt;can4.Look,someone is coming.Guess_.-Jack.Hes always on time.A.who can it be B.who he mayC.who he can be D.who it can be12第12页上一页首 页下一页5.I saw Mary in the library yesterday.-You_ her.She is still abroad.A.mustnt see B.cant have seen C.mustnt have seen D.couldnt see6.David,you _play with the valuable bottle,you_ break it.A.wont;cant B.mustnt;mayC.shouldnt;must D.cant;shouldnt13第13页上一页首 页下一页7.Susan refuses to marry Jack now.She _her mind.A.must change B.should have changedC.must have changed D.would have changed14第14页上一页首 页下一页8.Sue_ come together with us tonight,but she isnt very sure yet.A.must B.may C.need D.will15第15页上一页首 页下一页9.Aunt Margaret_ the train,otherwise she would have arrived here by now.A.must have missed B.should have missedC.had missed D.might miss16第16页上一页首 页下一页“情态动词情态动词+have done”不再对一件事情是否发生进行猜测,而是对已发不再对一件事情是否发生进行猜测,而是对已发生事表示自己看法,有时含有一定感情色彩。生事表示自己看法,有时含有一定感情色彩。ought to/should have done本该做(却未做);本该做(却未做);oughtnt to/shouldnt have done本不该做(却做了),含有本不该做(却做了),含有“责备责备”之意。如:之意。如:You shouldnt have done that;I had warned you of that several times.我我已屡次警告你,你本不该那么做。已屡次警告你,你本不该那么做。might have done本能够做(却没有),有时表示很委婉责备。如:本能够做(却没有),有时表示很委婉责备。如:You might have phoned me,though you were busy then.你再忙也该给我你再忙也该给我打个电话。打个电话。could have done本可能(却没有)如:本可能(却没有)如:He could have caught the early bus,but he was delayed by helping a stranger.他本能够赶上早班车;他是因为帮一个陌生人而晚点。他本能够赶上早班车;他是因为帮一个陌生人而晚点。would(not)have done本想做(却没做)本想做(却没做)/本不想做(却做了)本不想做(却做了)17第17页上一页首 页下一页情态动词情态动词+have+done”表表“原原来来应应该该”使使用用情情况况分分析析一、一、should have done过去原来应该过去原来应该 (而实际上并没有(而实际上并没有)should not have done 本不应该本不应该 而实际上却已经而实际上却已经”如如:1、We should have studied last night,but we went to the concert instead.我我们们昨昨晚晚本本应应学学习习,但我们却去看音乐会了。(实际上没有学习)但我们却去看音乐会了。(实际上没有学习)18第18页上一页首 页下一页二、二、could have done它表示它表示“过去原来能够过去原来能够”实际上没能做实际上没能做。如如1、I could have run 100 metres in 12 seconds.我原来能用我原来能用12秒钟完秒钟完100米米.(实际上没能)(实际上没能)2、If you could have finished the task in time,you could have been promoted.假假如如你你当当初初能能准准期期完完成成那那任任务务话话,你你可可能能已已提提升升了了(实际上没有被提升)(实际上没有被提升)19第19页上一页首 页下一页三、三、need not have done它表示过去已做事,实际上没有必要。它表示过去已做事,实际上没有必要。如,如,1、I need not have got up so early.我原来无须要那么早起床(我原来无须要那么早起床(实际上早已起床实际上早已起床)2、I need not have waited for the train for an hour.我原来无须要等一个小时火车。我原来无须要等一个小时火车。(实际上已经等了一个小时)(实际上已经等了一个小时)问题问题:would have donewould have done在什么情况下使用呢在什么情况下使用呢?20第20页上一页首 页下一页四、四、would have done 用在虚拟语气中用在虚拟语气中 表示与过去事实相反之假设结果,常与表示与过去事实相反之假设结果,常与if 条件句连用条件句连用。1、I would have helped you if I had known of your difficulties.要要是是我我当当初初知知道道你你们们窘窘境境,我我就就会会帮帮助助你你了了(而实际上没有帮助你)(而实际上没有帮助你)2、If it hadnt rained yesterday,we would have gone out for a walk.假如昨天没下雨,我们就去散步了。假如昨天没下雨,我们就去散步了。(实际上没有去)。(实际上没有去)。21第21页上一页首 页下一页Practice1.Mr White _ at 8:30 for the meeting,but he didnt turn up.A.should have arrived B.should arrive C.should have had arrived D.should be arriving22第22页上一页首 页下一页2.If he had been here yesterday,he _ this pop star.A.would meet B.would have metC.met D.must have met23第23页上一页首 页下一页3.It is hard for me to imagine what I would be doing today if I_ in love at the age of seven with the Melinda Cox Library in my hometown.A.wouldnt have fallen B.had not fallenC.should fall D.were to fall24第24页
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