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你好,同學(xué),很高興回答你的問題 正確答案： 助動(dòng)詞與情態(tài)動(dòng)詞最主要的區(qū)別之一是,助動(dòng)詞本身沒有詞義,而情態(tài)動(dòng)詞則有自己的詞義,能表示說話人對有關(guān)動(dòng)作或狀態(tài)的看法,或表示主觀設(shè)想.例： 情態(tài)動(dòng)詞沒有人稱變換,后面接原形. What have you been doing since? (構(gòu)成完成進(jìn)行體,本身無詞義) I am afraid I must be going. (一定要) You may have read some account of the matter. (或許已經(jīng)) 除此之外,情態(tài)動(dòng)詞還有如下詞法和句法特征： 1) 除ought和used以外,其他情態(tài)動(dòng)詞后面只能接不帶to的不定式.如果我們把ought to和used to看作是固定詞組的話,那么,所有情態(tài)動(dòng)詞無一例外地只能接不帶to的不定式.例： We used to grow beautiful roses. I asked if he would come and repair my television set. 2)情態(tài)動(dòng)詞在限定動(dòng)詞詞組中總是位居第一.例： They need not have been punished so severely. 3)情態(tài)動(dòng)詞沒有人稱和數(shù)的變化.例： She dare not say what she thinks. 4)情態(tài)動(dòng)詞沒有非限定形式,即沒有不定式,、-ing分詞和-ed分詞形式.例： Still, she needn’t have run away. 5)情態(tài)動(dòng)詞的“時(shí)”的形式并不是時(shí)間區(qū)別的主要標(biāo)志.在不少場合,情態(tài)動(dòng)詞的現(xiàn)在時(shí)和過去時(shí)形式都可以表示現(xiàn)在,、過去或?qū)頃r(shí)間.例：Would you mind very much if I ask you to do something? She told him he ought not to have done it. 6)情態(tài)動(dòng)詞之間是相互排斥的,即在一個(gè)限定動(dòng)詞詞組中只能出現(xiàn)一個(gè)情態(tài)動(dòng)詞,但有時(shí)卻可以與助動(dòng)詞have和be連用.例： You should have washed the wound. Well, you shouldn’t be reading a novel. 1. can與could 1) can可用于表示能力,、可能性,、允許等.例： She can sing that song in English. /Can the news be true? /Can I smoke here? 2)(用于否定句,、疑問句或感嘆句中)表示猜測,、懷疑或驚詫.例： She couldn't / can't be so stupid to do that . 2) can 只有兩種時(shí)態(tài),過去式為could. could 不僅用于過去,也可用于現(xiàn)在,表示委婉,、客氣,常用于疑問句,；而be able to 有較多的時(shí)態(tài)形式.be able to 的過去式表示“設(shè)法做某事”,經(jīng)過努力之后才完成的,而could 沒有這個(gè)含義.例： The fire spread through the hotel quickly, but everyone was able to get out. 2.may與 might 1)表示請求,、許可、允許,、可能性.例： The librarian told her that she might return the book to the library in three days. 當(dāng)回答由may 引起的問題時(shí),否定答語要用must not,表示“不許可”,、“不應(yīng)該”、“不行” .例：---May I come in? ---Yes, please. /--No, you mustn’t. 2)may (might) have done 表示對過去發(fā)生行為的推測,含有“想必”,、“也許是”的意 思.例： He might not have settled the question. 3.must與have to 1)must表示必須,、必要.例：We must protect people’s rights. 2)“must be 表語”的結(jié)構(gòu),通常表示猜測,含有“一定”之意.(只用在肯定句中)例： He must be an honest boy. “must have 過去分詞”的結(jié)構(gòu),常用在肯定句中,表示對過去發(fā)生行為的推測,含有“一定”、“準(zhǔn)是”的意思.否定和疑問句用can.例：It must have rained last night for it is so wet outside. 3)must 的否定式有兩個(gè)：當(dāng)回答由must引起的問題時(shí),否定答復(fù)要用needn’t或don’t have to 表示“不必”,、“無須”,、“用不著”、“不一定”的意義.當(dāng)表示“不應(yīng)該”,、“不許可”,、“禁止”時(shí),就用must not.例：—Must I go tomorrow? —Yes, please./Yes, you must. —No, you needn’t./No, you don’t have to. 4)have to 比較強(qiáng)調(diào)客觀需要,must著重說明主觀看法.例： I must clean the room.(主觀想法) I have to clean the room.(客觀需要) have to 能用于更多時(shí)態(tài).例：We had to be there at ten . have to 的否定式don’t have to do 表示“不必做……”之意. 4. ought to與should 1.ought to 1)表示“職責(zé)、義務(wù)”.例： Your son is still young. You ought to take care of him. 2)表示推測. 注意與must表示推測時(shí)的區(qū)別： He must be at 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) 這時(shí),ought to和should可以互相換用. 3)“ought to have 過去分詞” a. 表示“本應(yīng)該做,而實(shí)際沒有做某事”,相當(dāng)于should have 過去分詞.例： You ought to have asked him (but you didn’t). b. 表示“本不應(yīng)該做,而實(shí)際做了某事”.例： You oughtn’t to have stopped on the motor way.你本不應(yīng)該在高速公路上停車的. c.表示推論或推測某事已經(jīng)發(fā)生,含有說話人不能肯定其說法是否爭取的含義.例： If he had started at nine o’clock, he ought to have been in London by eleven o’clock. 如果她是酒店出發(fā)的話,那他十一點(diǎn)中該到達(dá)倫敦了. 4)ought to 可用于否定句, 疑問句,其否定形式可縮略為oughtn’t to.例： You oughtn’t to smoke so much. Ought you to smoke so much? 5)ought to的疑問式及其回答. ---They ought to do it,oughtn’t they? ---Yes,they ought(to). ---No,they oughtn’t . 在美國英語中,ought to用于否定句和疑問句時(shí),to可以省略.例： Ought you smoke so much? You oughtn’t smoke so much. 2.Should 1)should用于第一人稱疑問句中詢問對方的意愿,表示說話人的一種謙遜,、客氣,、委婉的語氣.例： What should we do now? 2)表示應(yīng)該,、必須,常與must 換用.例： We should (must) master a foreign language at least. 3)“should be 表語”的結(jié)構(gòu),表示推測或驚奇.例： They should be back by now. 4)“should have 過去分詞”的結(jié)構(gòu), 表示過去該做而實(shí)際上尚未做的動(dòng)作或行為；其否定則表示發(fā)生了不應(yīng)該發(fā)生的行為.其同義結(jié)構(gòu)“ought to have 過去分詞”,表示過去“早應(yīng)該”,、“本當(dāng)”之意,語氣較強(qiáng).例： I should have thought of that. 這一點(diǎn)我是應(yīng)當(dāng)想到的.(但沒想到) They should not have left so soon.他們不應(yīng)當(dāng)走得這么早.(但已走了) should表示勸告,、建議、命令,其同義詞是ought to,；在疑問句中,通常用should代替ought to.ought to表示“應(yīng)該”時(shí)和should差不多,只是口氣稍重一些, ?？苫Q用.ought to比should具有更強(qiáng)烈得道義、責(zé)任,、法律或原則等意味,；should指主觀上感到有責(zé)任或義務(wù)去做某事,語氣較婉轉(zhuǎn).例: You ought to keep your promise. You should apologize to him. 5. shall 與should 1)shall用于第一人稱征求對方的意見.例：What shall I wear on the journey? 2) 用于第二、第三人稱時(shí)表允諾,、命令.例：You shall come to my office immediately . 3)should用于第一人稱疑問句中詢問對方的意愿,但語氣較委婉溫和,例： What should we do now? 4)表示應(yīng)該,、必須,常與must 換用.例： We should (must) master a foreign language at least. 5) should 的其他用法請參閱上條ought to與should . 6. will與would 1)表示意志,決心或愿望.例： Surely we will support all the people in the world in their struggle for peace. If you will go,I shall go with you. 2)will表示經(jīng)常性、習(xí)慣性或傾向性,would表示過去的習(xí)慣行為.例： He will sit there hour after hour looking at the traffic go by. He would come to see me when he was in Beijing. 3)用于主語是第二人稱的疑問句中,表示對對方的請求,would的語氣比will委婉.例： Would/Will you kindly tell me the way to the station? 7. need 與dare need 與dare作情態(tài)動(dòng)詞用時(shí),一般用在否定句和疑問句中,如果用在肯定句中,多 數(shù)是實(shí)義動(dòng)詞,一般現(xiàn)在時(shí)單數(shù)第三人稱要加s,并有時(shí)態(tài)變化,后接不定式時(shí)須帶to.例： Need you go so soon? Dare you stay here alone in the night? Need I explain once more? 需要我再解釋一次嗎?(情態(tài)動(dòng)詞) The question needs to be discussed. 這個(gè)問題需要加以討論.(實(shí)義動(dòng)詞) She dare not tell the truth to him. 她不敢向他講真話.(情態(tài)動(dòng)詞) We should dare to think, to speak and to act. 我們應(yīng)該敢想,、敢說,、敢干.(實(shí)義動(dòng)詞) 錯(cuò)句：She dares not go out at night. He doesn’t need do that. Dare she to go there? 8. 注意推測性用法中謂語動(dòng)詞發(fā)生的時(shí)間 如果推測的為過去的事情,情態(tài)動(dòng)詞后要用完成形式.例： There must have been no one in, for nobody answered the phone. 如果推測的是正在進(jìn)行的事情,情態(tài)動(dòng)詞后則用動(dòng)詞的進(jìn)行形式.例： They must be talking about something very secret. 如果推測的是現(xiàn)在的狀態(tài)等,情態(tài)動(dòng)詞后則用動(dòng)詞原形.例：He must be badly ill. He looks so pale. 如果推測的是將來發(fā)生的事情,情態(tài)動(dòng)詞后同樣用動(dòng)詞原形,這時(shí),情態(tài)動(dòng)詞只能是may/might.例： There may be a terrible storm in the following few days. 肯定的推測一般用may, should, must,它們的意思分別是“可能”,“應(yīng)該”,“必定”,口氣逐漸加強(qiáng). 否定的推測常有兩種情況：口氣較弱,對否定不大有把握時(shí),用may not “可能不”；口氣比較強(qiáng),對否定比較有把握時(shí)用cannot,表示“不可能”.推測的疑問句,一般只用can/could, 例： Who can it be ? / Can it be true? 9.其它幾個(gè)“情態(tài)動(dòng)詞 動(dòng)詞的完成形式”并不表示推測,注意意義上的區(qū)別： could have done本來能夠,例： He didn't take part in the competition, he could have won, though. needn't have done 本來沒必要,例： You needn't have hurried. There was plenty of time. should/ought to have done 本來應(yīng)該,例： You should have told me earlier. I could have helped you. shouldn't/oughtn't to have done 本來不應(yīng)該,例： You shouldn't have been following him so closely; you should have kept your distance ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 希望能幫到你,祝更上一層樓O(∩_∩)O 不明白請繼續(xù)追問,可以詳談嘛(*^__^*) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
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