情态动词和虚拟语气专题1.doc

情态动词和虚拟语气专题情态动词的类型和特征:1. 情态动词的类型(1)只作情态动词的有:must,can (could),may(might),ought to ;(2)可作情态动词也可作实义动词的有:need ,dare (美语中常用作实义动词)(3)可作情态动词也可作助动词的有: shall (should),will (would);(4)具有情态动词的某些特征的有:have (had) to ,used to .二.情态动词的特征:1.有一定的词义,但不能单独做谓语,它们要和行为动词或连系动词连用,构成谓语.2.适用于主语的各种人称和数(have to 例外,主语是第三人称单数时,要用has to ).如:we /He must work hard .I have to walk home . He has to walk home .3.后面接动词原形,即不带to 的不定式(ought to ,have to ,used to 本身带有to).如:He maylose his way . You ought ot obey the law .4.具有助动词的作用,即可用来构成否定句,疑问句及用于简明答语.如: -I cant swim .(an you swim ? ) -No ,I cant either.二.情态动词用法要点: (一) 表能力:1.表示现在的或一般的能力:表现在的或一般的能力用can或be able to ,一般的能力即你无论什么时候想做就能做到的能力.表示现在的或一般的能力时,can tebe able to 更普遍.如:A computer cant think for itself ;it must be told what to do (一般能力) He is a native speaker of English ,so he can of course speak English quite well (一般能力) I am starving(挨饿) to death . I can eat two bowls of rice now .(现在的能力)2.表示将来的能力:表示将来的能力用will be able to .如:If you have a good sleep ,you will be able to work out this problem .3. 表示过去的能力 (1) could ,was/were able to 表示过去一般的能力,但不表示做或未做某事;(2)was /were able to 表示过去有能力,并且成功地做了某事,相当于managed to do something /succeeded in doing something;(3)“could have +过去分词”表示过去有能力做,但未做.如:She could /was able to sing like an anged when she was a child (过去一般的能力) I could have worked out the problem ,but I didnt (过去有能力做但未做)训练题: 1.I should have been there ,but I not find the time .A.would B.could C.might D.should2. I stayed at a hotel while in New York . Oh ,did you ? You with Barbara .A.could have stayed B.could stay C.would dtay D.must have stayed3. The fire spread through the hotel very quickly but everyone get out .A.had to B.would C.could D.was able to二.表推测(可能性)1.可能性可分为客观的可能性,和具体事情实际发生的可能性两种,所谓客观的(理论的)可能性,即不涉及具体某事是否会发生,此种用法常常可以说明人或事物的特征.情态动词can 可用于肯定句中表示客观的(理论的)可能性,而表示具体事情实际发生的可能性时, can一般不用于肯定句.如:Accidents can happen on such rainy days .这样的多雨天可能会发生事故.(客观的可能性).2.表示具体事情实际发生的可能性: (1)表示具体事情实际发生的可能性的层次比较(见下表):词形肯定式否定式疑问式must必定,必然/Will很可能,大概不会,不该会.吗?Would可能性比will小语气比wont弱语气比will弱Should说话者有较大的试探性结果/Ought to说话者有较大的试探性(含义同should)/Can/不可能有可能吗?Could微弱的可能性不可能语气比can弱May或许,也许,也未可知,也说不定可能不/might比may还弱比may not还弱/(2)表示具体事情实际发生的可能性时,may ,must 常用于肯定句,一般不用于否定句,疑问句(may not 表示“可能不”),can 常用于否定句,疑问句或感叹句中,表示疑惑,惊讶或不相信等意思;could 既可用于肯定句又可用于否定句，疑问句中。如：This cant /couldnt be done by him (这不可能是他干的。) （表不相信）This may not be done by him . 这不可能不是他干的。（表不确定）He could be on his way home now . 他现在可能在回家的路上了。（could 不如may /might常用 ） （an this be done by him? ）这可能是他干的吗？ （表示疑惑，惊讶）Mr Bush is on time for everyghing .How can it be that he was late for the opening ceremony ? （表示疑惑，惊讶）I didnt hear the phone . I must have been asleep .(表肯定)-Are you coming to Jeffs party ? -Im not sure .I might go to the concert instead .(表示不确定)。训练题：用can,could,may ,might ,must 填空:4.Is Johu coming by train ? -He should ,but he not .He likes driving his car .5.Peter come with us tonight ,but he isnt sure yet .6. Sorry Im late , I have turned off the alarm clock and gone back to sleep again .7.That not be Mary . Shes in hospital .8. How you be so stupid?(3).Would ,could ,should ,might 并不一定与过去时间有关，而表示可能性，弱于它们相应的表现形式。如：This may /might be done by him .这件事可能是他干的。（证据依次递减）（4）should 表推测时，表示确定或可能有的未来或期望，即合乎理想的情况或结果。如：He should be around sixty years old .他可能60岁上下。（表确定）He ought toe home by now .他现在该到家了。（表确定或期待）Its nearly seven oclock .Jack should be here at any moment (表确定或期待).-When can I come for the photos ? I need them tomorrow afternoon?They should be ready by 12:00(表期待)。三表示 请求，允许，允诺。1.当对方是决策者时，你代表你（们）自己（I ,we）,或代表第三者（he ,she ,they）向对方（you）请求或提出建议时用，（1）Shall/May (Might)/can (could )/I /we ?(2) Shall he /she /they ?(3)Would /will you ?如Shall we begin our class ?shall the driver wait outside ?When shall my father be able to leave hospital?Can/could I leave now ?Would you do me a favor ?1. could/might /would /should 表委婉的功能。如-Could /might I use your bike tomorrow morning ?-Yes ,you can /may (否定：No ,Im afraid not )不可说：Yes,you could /might . 回答允许时；用could /might 表委婉是不恰当的。如：- Could I borrow your dictionary ? Yes,of course ,you can .训练题：（9）-The room is so dirty . we clean it ? -of course .A.Will B.Shall C.Would D.Do(10) - he come to see you ? -of course ,please .And Id rather he told me the truth .A.Will B.Shall C.Would D.Do3.当你自己（I）是决策者时，给对方（you）或第三者（he ,she ,they ）以命令，警告，允诺或威胁时，要用shall.此外，当颁布法律，规定时，也要用shall.如：You shall get out at once ,and he also shall (=I order you and him to get out at once ) 你马上给我滚出去！他也一样。（说话者的意志）It has been announced that candidates shall remain in their seatw until all the papers have been collected .（规则或规定）在所有试卷收一来之前，应试者必须留在座位那里。训练题 ：（11）He asked kme for this book many times ,please tell him he have it tomorrow .A.must B.cay C.shall D.both （B and C）(12)It has been announced that all the students puton masks (口罩) before going to school in case they are inf e cted with SARS virus .A.shall B.will C.need D.may四表示必要性：must 常用来表示必要性，意为“必须”。表示现在或将来必须做某事用must+动词原形，表示现在或将来不必做某事时，用dont have to do sth或dont need to dosth 或neednt do sth ;表示过去没必要做某事时，分为以下情况 ：1.当表示过去没必要做某事，但事实上却做了，用neednt have done sth .2.当表示过去没必要做某事，而不涉及是否做，可用didnt have to do sht 或didnt need to do sth 或It was not necessary to dosth 等。如：You neednt have worked that late last night .It was harmful to your health .-Did you work very late last night ? -NO ,I didnt .I didnt need to work very late .should 表必要性，在语气上比must (必须)弱。Should +动词原形，表示现在或将来应该做某事（的必要性）。Should +have +过支分词，表示过去本该做某事（的必要性）。如：I should go and visit him this afternoon,but I wonder I will be free (表示将来的必要性)You should have come to the conference (会议)yesterday ,What was your absence?(表示过去的必要性)。训练： 13 You _(没必要告诉) her the news,for I had told her about it earlier .14 _(没必要非得出去) but I wanted a breath of fresh air ,15 We _(本该买) a new lock for the frowt door ,五表示“宁愿做某事”时，可使用下面这些句式：Would rather do sth , would rather do sth than do sth, would do sth rather than do sth , would rather sb did sth ,prefer todo sth ,prefer to do sth rather than do sth, prefer doing sth to doing sth,六情态动词+have done 用法：Must have done 表示对过去已经发生地行为进行推测，意为“想必/准是/一定做了某事”。如：It must have rained last night ,for the road wasQuite must have rained last night , for the road was quite muddy,The lights were out,They must have been as leep. Can have done 表示对过去发生的行为的怀疑和不肯定，通常用在否定句和疑问句中。如：He cannot Have forgotten it ,Can he have gone to his aunts?could have done 可用于肯定句中，表示“可能已经-”之意，此外还可以表示过去没有实现的可能性，意为“本来可以-”。如You could have done better ,but you Were careless,I saw Mr wang just now ,He couldnt have gone to beijing.May /might have done 表示对过去已发生的行为的推测，意为“也许/或许已经（没有）-“，一般只用于肯定句或否定句中（在否定句中表示”可能不“）不用于疑问句，用 might则表示语气更加不肯定，如:Its to late ,I think he may have gone to bed ,He may not have finished the work, She might have caught a cold. Might have done 表示“本来可能-”但实际上没有发生的事。另外还可以表示“本来应该或可以做某事-之意，含有轻微的责备语气。如：You should not have swum in that sea ,You might have been eaten by fish ,You might have given more help ,though you were busy.Should /ought to have done 用于肯定句时，表示“本应该做某事，而实际上未做”，用于否定句时，则表示“不应该做的事反而做了”。如： I told her friend how to get to the hotel ,but perhaps ,I should have driven her there ,You ought to have done this exercise more carefully. You shouldnt have toldher the truth , He ought not to have treated his parents Like that . neednt have done 表示“做了本来不必去做的事”，注意： Didnt need to do 表示“没必要做而实际上也没有做某事”。You needntHave taken a taxi here ,for it was very near to my house, I didnt need to clean the windows. My brother did it . had better have done 用于事后的建议，含轻微责备的口吻，意为“当时最好做了某事，”其否定形式 Had better not have done 表示相反的含义。如：You had better have started ear lier.You had better not have scolded her .Would rather have done 表示 “当时宁愿须知某事，”其否定式would rather not have done 表达相反含义，两者都表示 “后悔”之意。如：I would rather have taken his advice .I raised objections at the meeting ,but now I would rather not have done that .Would like /love to have done .表示过去愿意做某事，但未做成。如：I would /love to have gone to the party last night but I had to work extra hours to finish a report .训练： （16）I told sally how to get here ,but perhaps I for her .A.had to write it out B.must have written it out C.should have written it out D.ought to write it out (17)I was really anxious about you .You home without a word .A.mustnt leave B.shouldnt have left C.couldnt have left D.neefnt leave(18)He hesitated for a moment efore kicking the ball,otherwise he a goal .A.had scored B.scored C.would score D.would have scored 七情态动词其它用法要点：1.cannot but +do sth 表示“不得不；只好”。如：I can not but choose to go . 我只好去。2.may well 和may as well 结构：“may well +动词原形”，是一种常用结构，意为“完全能，很可能，”相当于to be very likely to .如：He may well be priud of his son , 他大可为儿子感到自豪。Her appearance has changed so much that you may well not Recognize her , “may as well+动词原形“意为最好，满可以，到不如，”相当于had better 或to have no strong reason not to 如：You may as well do it at once ,We may as well stay wlure we are 我们留在现在的地方倒是不错。3.cannot (或never 等否定句)与enough连用表示“再。也不为过”具体的用法见例子：You cannot be careful enough 你再细心也不为过。I cant thank you much enough. I cant thank you too much 我太感谢你了。4.may 可以用于祈使句表示祝愿。如 ：May we never forget each other 愿我们彼此永不相忘。May you return in safety.愿你平安归来。5.Why/How +should 结构表示说话人对某事不能理解，感到意外，惊讶等意思，意为“竟会”如：Why should you be so late todaay?你今天怎么会来的这么晚？How should I know? 我怎么会知道？（意为我不知道）.训练：19. 我不得不钦佩你的勇气。（cannot but _）_20. 她很可能拒绝和你谈话。（may well）_21. 你最好留在这里过夜，（may as well）_22. 祝你的生活美满，幸福。（may）_23. 祝你成功！（may）_24. 我真不明白你凭什么认为这件事