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情態(tài)動詞的用法,情態(tài)動詞表示說話人對某一動作或狀態(tài)的情感和態(tài)度。 情態(tài)動詞沒有人稱和數(shù)的變化。 但不能單獨(dú)作謂語動詞用，必須動詞原形一起構(gòu)成謂語動詞。 將情態(tài)動詞置于主語之前即構(gòu)成其疑問式，在情態(tài)動詞之后加not既構(gòu)成其否定式。,1.can和could (could為can的過去式) (1)表示能力，eg： He can speak English better than you. (2)在疑問句和否定句中表示“懷疑”、“猜測”或“可能性”，eg： Can this green bike be Liu Dong‘s? (3)表示“許可”時can可以和may換用 eg:You can (may) go home now.,(4)如果要表示語氣婉轉(zhuǎn)，可用could代替can，這時could不再是can的過去式 eg:Could you come again tomorrow? (5)can和be able to都可表示能力。但是can只能有現(xiàn)在式和過去式，而be able to則有更多的形式，如： eg:He will be able to do the work better.,2、may和might (1)表示允許或征詢對方許可意為“可以” You may use my dictionary. 在回答對方說“可以做或不可以做某事”時，一般多不用may或 may not，以避免語氣生硬或不容氣。而用比較婉轉(zhuǎn)的說法進(jìn)行回答。 eg：---- May I use this dictionary? --- Yes, please. ---- Certainly.,在請求對方許可時，如果Might I…? 就比用May I…? 語氣更婉轉(zhuǎn)些，如：May I have a look at your new computer? 但是表示“阻止”或“禁止”對方做某事時，要用must not代替may not， ---- May we swim in this lake? ---- No, you mustn’t. It’s too dangerous.,(2)may或 might都可以表示可能性，表示“或許”、“可能”之意，如果用might表示可能性，則語氣更加不肯定， eg：They may (might) be in the library now .,3、must的基本用法 (1)must表示“必須”，其否定式 must not，縮寫形式為 mustn’t，表“不準(zhǔn)”、“不許可”或“禁止”之意， eg: We must study hard and make progress every day. You mustn't touch the fire.,(2)對以must提出的疑問句，如作否定回答時，要用needn’t或用don’t (doesn’t) have to (不 必)來回答，而不用mustn’t eg：---- Must we finish the work tomorrow? ---- No, you needn’t (don’t have to), but you must finish it in three days.,(3)在肯定句中must可以表示推測，表示“一定”或“必定”之意， eg：---- Whose new bike can it be? ---- It must be Liu Dong's. I know his father has just bought him a new one.,4、can, could, may, must后接完成式的用法 (1)can, could后接完成式的用法： ①在否定句或疑問句中表示對過去發(fā)生過的事情的“懷疑”或“不肯定”的態(tài)度，Could he have said so? ②在肯定句中，可以表示過去可能做到而實(shí)際并沒做到的事情，有“勸告”或“責(zé)備”的語氣。,如：---- When did you answer her letter? ---- Only yesterday. ---- It's too late. You could have answered it earlier, I am sure.,(2)may, might后接完成式的用法 ①表示對過去某事的推測，認(rèn)為某一件事情在過去可能發(fā)生了。 eg：Mary might have learned some Chinese before. ②可以表示過去本來可以做到而實(shí) 際沒有做到的事情，有“勸告”或“責(zé)備”的語氣,eg：You didn't do the work well that day. You might have done it better. (3)must后接完成式的用法：表示對過去某事的推測，認(rèn)為某事在過去一定做到 了。 如：Liu Dong isn’t in the classroom. He must have gone to the library.,5、have to 的基本用法：意義相近，只是 must側(cè)重表示說話人的主觀看法，而have to 則表示客觀需要， eg：I must study hard. I had to give it up because of illness.,6、ought to的基本用法 (l)表示根據(jù)某種義務(wù)或必要“應(yīng)當(dāng)”做某事，語氣比should強(qiáng)， eg：Everyone ought to obey the traffic regulations.,(2)表示推測，注意與must表示推測時的區(qū)別： He must be home by now .(斷定他已到家)， He ought to be home by now .(不十分肯定) This is where the oil must be.(比較直率) This is where the oil ought to be. (比較含蓄) ；,(3)“ought + have+ 過去分詞”表示過去應(yīng)做某事而 實(shí)際未做。 eg：You ought to have helped him. 這時，ought與 should可以互相換用。 注意，在美國英語中ought to 用于否定和疑問句時to可以省略。例如：Ought you smoke so much? You oughtn’t smoke so much.,7、dare的基本用法 (l)dare (dared為其過去式) 作情態(tài)動詞用時，主要用于否定句，疑問句和條件從句中。 eg：Dared he break the traffic rules again? (2)在現(xiàn)代英語中dare常用作行為動詞，其變化與一般行為動詞相同， eg：She dares to stay at home alone at night.,8、need的基本用法 (1)need作情態(tài)動詞用時，主要用于否定句和疑問句中， eg：He needn't worry about us now. (2)need也可作為行為動詞用，可用于肯定句，否定句和疑問句中，其后可接名詞、代詞、動名詞或帶 to 的動詞不定式為其賓語。,eg：You need to practise reading aloud every day. (3)needn‘t后接完成式可以表示過去做了一件本來不必要做的事情， eg: ---- Did you answer the letter yesterday? ---- Yes, I did. ---- But you needn’t have answered it.,9、shall的基本用法 (1)shall用作情態(tài)動詞時，用于第二、三人稱，表示說活人的意愿，可表示“命令”、“警告”、“強(qiáng)制”、“威脅”或“允諾”等意。 eg：He shall go first, whether he wants to or not. (2)在疑問句中，shall用于第一、三人稱，表示說話人的征詢對方意見或請求指示。 eg：Shall I open the door?,10、should的基本用法 (1)should作為情態(tài)動詞可以表示“建議”或“勸告”，有“應(yīng)該”之意，eg：You should learn from each other. (2)should后接完成式表示過去沒有做到本來應(yīng)該做的事情，或是做了本來不應(yīng)該做的事情。eg：You should have given him more help.,11、will的基本用法 (1)用于各種人稱，可以表示“意志”或“決心”，eg：I have told him again and again to stop smoking, but he will not listen. (2)在疑問句中用于第二人稱，表示說話人向?qū)Ψ教岢稣埱蠡蛟儐枌Ψ降囊庠?eg：Will you please tell me how to get to the Capital Gymnasium?,(3)will可以表示一種習(xí)慣性的動作，有“總是”或“會要”之意， eg：Every morning he will have a walk along this river. 12. would的基本用法 (1)would作為will的過去式，可用于各人稱，表示過去時間的“意志”或“決心” 。eg：He promised he would never smoke again.,(2)在疑問句中，用于第二人稱，表示說話人向?qū)Ψ教岢稣埱蠡蛟S可對方的意愿時，比用will的氣更婉轉(zhuǎn) eg：Would you like some more coffee? (3)在日常生活中，用“I would like to…”表示“我想要”或“我愿意”之意，以使語氣婉轉(zhuǎn)。 eg：I would like to do Ex.2 first.,(4)would可以表示過去的習(xí)慣動作，比used to正式，并沒有“現(xiàn)已無此習(xí)慣”的含義。如： Last year our English teacher would sometimes tell us stories in English after class. During the vacation he would visit me every week. (5)表料想或猜想，如:,It would be about ten when he left home. What would she be doing there? I thought he would have told you about it. 13. used to, had better, would rather (1)used to表示過去的習(xí)慣動作或狀態(tài)，現(xiàn)在已不存在，在間接引語中，其形式可不變，例如： He told us he used to play foot ball when he was young.,否定疑問句： Usedn’t you to？Didn’t you use to be interested in the theatre? 強(qiáng)調(diào)句：I certainly used to/ did use to smoke, but it was a long time ago. 其反意疑問句或簡略回答中，也有兩種形式： Used you to get up early in the morning? Yes, I did./ used to.,Did you use to play chess? Yes, I did. Used you to get up early in the morning? Yes, I did./ used to. (2)had better意為“最好”，后接不帶to的不定式。 eg: ---- We had better go now . ---- Yes, we had (we'd better/ we had better).,Hadn’t we better stop now? Had we better not stop now? I think I’d better be going. (用于進(jìn)行時態(tài)，表“最好立即”) You had better have done that (用于完成時態(tài)，表未完成動作) 注：had better用于同輩或小輩，對長輩不可用,(3)would rather意為“寧愿”。 I’d rather not say anything. Would you rather work on a farm? ---- Wouldn’t you rather stay here? ---- No, I would not. I’d rather go there.,由于would rather表選擇，因 而后可接than。 eg: I would rather work on a farm than in a factory. I would rather watch TV than go to see the film. I would rather lose a dozen cherry trees than that you should tell me one lie.,