情態(tài)動詞與虛擬語氣知識點講解

1、情態(tài)動詞與虛擬語氣I.情態(tài)動詞基本用法情態(tài)動詞cancouldmaymightmusthave to用 法能力（體力，智力，技能）允許或許可（口語中常用）可能性（表猜測，用于否定句或疑問句中）可以（問句中表示請求）可能，或許（表推測）祝愿（用于倒裝句中）必須，應(yīng)該（表主觀要求）肯定，想必（肯定句中表推測）只好，不得不（客觀的必須，有時態(tài)和人稱的變化）否定式疑問式簡答式can not / cannot/can tdoCan do?Yes, can.No, can t.couldn t domay not doMay do?Yes, may.No, mustn t/can t.might not

2、doMight do?Yes, mightNo, might not.Yes, must.must not/mustn t do Must do ? to.No, needn t/don thavedon t have to doDo have to doYes, do.?No, don t.ought）ought not to/oughtn tYes, ought.應(yīng)當(dāng)（表示義務(wù)責(zé)任， 口語中多用 shouldto doOught to do?toNo, oughtn t.用于一三人稱征求對方意見、二三人稱許Yes, shall.shallshall not/shan t do Shall

3、do?諾、命令、警告、威脅等No, shan t.應(yīng)當(dāng)，應(yīng)該（表義務(wù)責(zé)任）should not/shouldnShtdould do?should本該（含有責(zé)備意味）will意愿，決心請求， 建議，用在問句中would 比較委婉woulddare敢（常用于否定句和疑問句中）need需要 ,必須（常用于否定句和疑問句中）used to過去常常（現(xiàn)在已不再）will not/won t doWill/Would doYes, will.would not/wouldn?No, won t. t dodare not/daren t doYes, dare.Dare do?No, daren t.n

4、eed not/needn t doYes, must.Need do?No, needn t.used not/usedn t/usen tYes, used.? No, use(d)n t.Used to doto doDid use to do?Yes, did.didn t use to doNo, didn t.精選文庫II.情態(tài)動詞的重點知識A computer_think for itself; it must be told what to表示能力的情態(tài)動詞用can/coulddo.A.can t B.mustn t C.may notD.might not CouldIcal

5、l you by yourfirst name? Yes,表示許可時用 may/might ,can/could 都可以，you_表示“能A.will B.couldC.may D.might但在問句中用 could ?或 might ？以使口氣委力、許可 ”can 或 may，以使回 Johnny,you_play with the knife, you_hurt的 can婉客氣，其回答一定要用和 答口氣明確（ must 表示一定，必須， mustntmayyourself.表示禁止，不許可） 。A.won t/can t B.mustn t/mayC.shouldn t/must D.ca

6、n t/shouldn t在肯定句中 could 不可以用來表示過去某一特定場合的能力，而要用 was/were able to 。在肯定句中都可以用來表示可能。在含義上must 語氣最肯定 ,may 表示的是事實上的可能性。表示“推斷、判斷”的 can在否定句中只能用can 和 may。所以 cant時may,must用以代替mustnt，語氣比may 更肯定。中文可以翻譯為不可能。The fire spread through the hotel very quickly buteveryone_get out.A.had toB.wouldC.couldD.was able toPete

7、r_come with us tonight, but he isn t very suyet.A.mustB.mayC.canD.will而 can 表示的是邏輯上的可能性：Mary is in poor health. She can be ill at any times.Michael_be a policeman, for he s much too short.A.needn tB.can t C.shouldD.mayneeddareshall在疑問句只能用He may be very busy now.Can he be very busy now?can，不能用 may 和

8、must。Can he be very busy now?He must be very busy now.need 作為情態(tài)動詞只有一種形式，只用于否定句和疑問句。dare 作為情態(tài)動詞用時有兩種形式：If he dare come,I will kick him out. I don t know whetherdare 和hedared 兩個詞形，除了可以用于否定句和疑問dare say.句外，還可以用于條件從句或表示懷疑的句子中。注意 :He doesn t dare(to)answer the question.（否定句）Does she dare(to)enter the dark

9、 room? （疑問句）用于第一人稱：征求對方的意見。What shall we do this evening?You shall fail if you don t work警告harder.用于第二、三人稱：警告、命令、允諾、威脅He shall have the book when I finish reading. 允諾等。He shall be punished. 威脅should勸告、建議、命令、應(yīng)該做、道義上的責(zé)任。You should(ought to) go to class right away.-2請求、建議，would 比 will 委婉客氣。表示意志、愿望和決心。精

10、選文庫I should(ought to) help him because he is in trouble.Would you pass me the book?I will never do that again.They asked us if we would do that againwill/would情態(tài)動詞+havedone 的用法would 可表示過去反復(fù)發(fā)生的動作或某種傾向。would 表示估計或猜想。could+have done ：本可以做而實際上未能做。cannot+ have done ：表示對現(xiàn)在或過去行為的否定推測。can+主語 + have done ：表示

11、對過去行為的懷疑或不肯定（用在疑問句中） 。might(may)+ have done ：對過去發(fā)生的行為不太肯定的推測。must+ have done ：對過去發(fā)生的行為肯定的推測。其否定式為：cannot have done 。During the vacation he would visit me every week The wound would not heal. （傷口老是不能愈合）It would be about ten when he left home.What would she be doing there?You could have done better, b

12、ut you didn t try your beHe cannot have been to that town.Can he have got the book?He may not have finished the work.If we had taken the other road, we might have arrived earlier.You must have seen the film.You cannot have seen the film.You needn havet watered the flowers,for it is going to rain.nee

13、dn t+ have done：本來不必要做的而實際上又做了。should(ought to)+ have done ：本來應(yīng)該做而實際上又沒有做。 其否定形式表示某中行為不該發(fā)生卻發(fā)生了。注意： didn t need to(have to)do：沒有必要做而實際上也沒有做I didn needt to clean the windows.My sister did it 2 hours ago.You should have started earlier, but you didn t.She shouldn t have taken away my measuring tape,for

14、 I worked to use it.注意： He should have finished the workby now .（表推測）-3精選文庫虛擬語氣類別用法例句與 現(xiàn) 在從句動詞：過去式（be 用 were）事 實 相主句動詞：If he were here, he would help us.反should/would/could/might+doIf 引 導(dǎo)與 過 去從句動詞： had+done的事 實 相主句動詞：If I had been free,I would have visited you.條件從反should/would/could/might+have+done句

15、與 將 來從句動詞：過去式/should+ 動詞原形事 實 相 /were+to doIf it should rain tomorrow, we would not go camping.反主句動詞： should/would/could/might+動詞原形省 略 if將虛擬條件從句中的were， had,should 放到主 Should he come ,tell him to ring me up.的 虛 擬 Were I you,I would not do it.語之前，構(gòu)成主謂倒裝條件句H ad I been free,I would have visited you. If

16、he had listened to me, he would not be in troublenow.不同時間的虛擬：各遵守各的規(guī)則 If he had told me yesterday,I should know what to do混 合 虛now. If I were you, I would have gone to her birthday party.擬 條 件句 He could have passed the exam,but he wasncarefultenough.虛擬與陳述的混合：各遵守各的規(guī)則 You should have come earlier.The b

17、us left a momentago.but for+ 名詞表示虛擬條件含 蓄 虛擬句子或主句中的謂語動詞的形式視具體情況而定。這是考查考生應(yīng)變能力的最佳試題。-Butforyourtimelywarning,we_into great trouble.-You know we re friends.A. would getB. must have gotC. would have gotD. can t have got條件句without+ 名詞表示虛擬條件動詞不定式表示虛擬條件Without the air to hold some of the sun's heat, the

18、 earth at night would be freezing cold.It would be only partly right to follow in this way.如果用這種方式，僅僅對了一半?，F(xiàn)在分詞表示虛擬條件Having knownintime,wemighthavepreventedthe-4過去分詞表示虛擬條件精選文庫accident.要是及時得知的話，我們也許能阻止這場事故。Given more attention, the tree could have grown better.如果多留心的話，這樹本來可以長的更好。副詞 otherwise 表示虛擬條件連詞

19、but 連接的句子表示虛擬條件I was too busy at that time.Otherwise,I would have called you.我當(dāng)時太忙，否則我就給你打電話了。He _fatter but he eats too little .A. would become B. would have become C. must become D. must have become其它狀 語 從句賓 語 從句主 語 從句as if/as though 引導(dǎo)的狀語從句中動詞用did 或had done 或 would could might do。注意： as if/as tho

20、ugh 引導(dǎo)的狀語從句中也可以用陳述語氣：當(dāng)說話者認為所述的是真實的或極有可能發(fā)生或存在的事實時：It sounds as if it is raining 聽起來像是在下雨。 He talks as if he is drunk 從他談話的樣子來看他是醉了。in order that/so that 引導(dǎo)的狀語從句中動詞用 can/could/may/ might/ would 等 +dodemand, suggest, order, insist 后接的從句中動詞為 should+dowish 后的從句中分別用過去式，過去完成式和 should/would+do 表示與現(xiàn)在，過去和將來情況相反在 It is necessary / important / strange thatIt i