第5講 情態(tài)動詞情態(tài)動詞表示說話人的語氣和情緒，本身詞義不全，不能單獨作謂語，后面必須與動詞原形一起構(gòu)成謂語。情態(tài)動詞沒有人稱和數(shù)的變化，有的情態(tài)動詞有過去式。常見的情態(tài)動詞有can, could, may, might, must, have to, shall, should, will, would, ought to, need, dare, used to等。一、情態(tài)動詞的基本用法(一)can, could的用法【完成例句】(1)他媽媽會說法語。His mother can / could speak French.【結(jié)論1】表示體力或腦力(知識、技能)所產(chǎn)生的能力。【翻譯句子】(2)Man can / could not live without air.人沒有空氣不能呼吸?！窘Y(jié)論2】 表示客觀的可能性?！痉g句子】(3)Could you wait a few days for the money?錢你可以再等幾天嗎？(4)Could you be here at eight o'clock tomorrow morning?你能明天早上8點鐘到這兒嗎？【結(jié)論3】表示請求、建議，用could 比 can語氣更委婉(回答用原形)?！痉g句子】(5)Could / Can I borrow your reference books?我可以借下你的參考書嗎？(6)You can smoke in the entrance hall.你可以在入口大廳抽煙?！窘Y(jié)論4】表示允許、許可，用could 比 can更委婉客氣?！疽呻y1】Can it be true?You can't be serious!Oh, dear, what on earth can this mean?【疑難剖析1】否定句、疑問句和感嘆句中，can表示懷疑、驚異、不相信的態(tài)度?！疽呻y2】They were able to put out the fire without any help from the firefighters.【疑難剖析2】 表示“經(jīng)過努力后終于能”，用be able to?！疽呻y3】You can not be too careful.【疑難剖析3】慣用形式“can not (can't)too / over / enough”表示“無論怎么也不(過分)”，用來加強語氣?！疽呻y4】I couldn't but choose to wait.【疑難剖析4】cannot but do sth. 不得不；只好(二)may, might的用法【例句觀察】May I ask you a question?Might I close the window?You mustn't speak like that to your mother.【結(jié)論1】 表示允許、請求。Might I ？ 比 May I ？ 語氣更委婉和有禮貌?！痉g句子】(7) He might come tomorrow.他可能明天來。(8) He may be very busy these days.他這些天可能很忙?！窘Y(jié)論2】表示可能性，表示“或許，大概”。用于肯定句或否定句中，用might 比 may語氣更加不肯定?！疽呻y1】Study hard that you may work better in the future.They set out early so that they might arrive in time.【疑難剖析1】用于目的狀語從句中，含“為了”或“以便”之意?！疽呻y2】If that is the case, we may as well try.Now that they were all here, she might as well speak her mind.【疑難剖析2】 慣用形式 may (might)as well動詞原形：不妨做【疑難3】May you succeed!May the friendship between us last forever!【疑難剖析3】表示祝愿。(不用might)采用部分倒裝語序：may主語動詞原形(三)must，have to的用法【完成例句】(9)所有人必須遵守條例。Everybody must obey the rules.(10)不準你和你媽媽那樣說話。You mustn't speak like that to your mother.【結(jié)論1】must 表示“必須”。強調(diào)主觀看法，只有現(xiàn)在時形式，否定式是must not (mustn't)，表示“禁止”，“不準”?！痉g句子】(11)走了很遠的路你一定餓了。You must be hungry after the long walk.【結(jié)論2】must表示有把握的推測，意為“一定，肯定”，用于肯定句中。【翻譯句子】(12 )因為他的腿斷了，他不得不躺在床上。As he had broken his leg, he had to lie in bed.【結(jié)論3】have to表示“必須，不得不”，著重強調(diào)客觀需要，能用于更多時態(tài)(過去式和將來式)?！疽呻y】 How old are you, madam? If you must know, I'm twice my son's age.【疑難剖析】must有“偏要、硬要”之意。(四)will, would的用法【例句觀察】I will do my best to help you.我會盡力幫你的。He said that they would help us.他說他們會幫助我們的?！窘Y(jié)論1】用于各種人稱，表示意志或決心。will指現(xiàn)在，would則指過去?！就瓿衫洹?13)你可以教我怎樣駕車嗎？Would you teach me how to drive a car?(14)當你看見他能給他捎個便條嗎？Will you please give him a message when you see him?【結(jié)論2】用于第二人稱的疑問句中表示有禮貌的詢問和請求，would 比 will更委婉?！就瓿衫洹?15)魚沒水就會死。Fish will die without water.(16)星期天當他在北京的時候就會來看我。He would come to see me on Sunday when he was in Beijing.【結(jié)論3】表示習慣性、經(jīng)常性、傾向性，意為“總是”，“慣于”。 will指現(xiàn)在，would是指過去?！疽呻y1】That will be the man you want to see.Perhaps she would be willing to meet us.【疑難剖析1】表示說話人的推測，意為“大概，也許”。would 的肯定性不如will強，語氣比較弱?！疽呻y2】That will do.The machine won't work.He tried the door again, but it wouldn't open【疑難剖析2】. 表示功能，譯作“能”或“行”?！疽呻y3】would 與used to 的區(qū)別：We would sit in the yard every evening and listen to his story. (過去常有的習慣，但言下之意是現(xiàn)在可能還有這樣的習慣。)We used to sit in the yard every evening and listen to his story. (過去常有的習慣，但言下之意是現(xiàn)在沒有這樣的習慣了。)There used to be a park here.【疑難剖析3】used to表示過去的某種習慣，現(xiàn)在已經(jīng)沒那樣的習慣了；would 表示過去有某種習慣，現(xiàn)在可能還有。表示過去的狀態(tài)，只能用used to，不能用would。(五)shall, should, ought to的用法【翻譯句子】(17)我可以把燈關(guān)掉嗎？Shall I turn off the light?【結(jié)論1】shall用于第一、第三人稱作主語的疑問句中，表示征求對方的意見。【翻譯句子】(18) You should keep your promise.你應(yīng)該信守諾言?！窘Y(jié)論2】should意為“應(yīng)該”，表義務(wù)、責任，也可表示勸告、建議?！痉g句子】(19)媽媽現(xiàn)在應(yīng)該回來啦。Mother should be back by now.【結(jié)論3】 should表示按常規(guī)、常理推測，意為“可能”或“應(yīng)該”?！痉g句子】(20) I should think you are mistaken.我倒認為你是錯的?！窘Y(jié)論4】提出意見、建議時，可用should表示委婉、謙遜的語氣，意為“可”，“倒是”?！痉g句子】(21)你應(yīng)該在回家前完成作業(yè)。You ought to finish your work before you go home.【結(jié)論5】ought to表示責任和義務(wù)“應(yīng)該”，語氣比 should強；還可表推測。例如：You have practiced for a long time. There ought to be no difficulty for you.【疑難1】You shall go with me.You shall not leave your post.【疑難剖析1】shall用于第二、第三人稱作主語的陳述句中，表示說話人的決心、意志、許諾、命令、警告、威脅等。【疑難2】Why should you be so late?你今天來得怎么這么晚？How should I know?我怎會知道！(意為：我不知道。)【疑難剖析2】Why / How should結(jié)構(gòu)表示說話人對某事不能理解，感到意外、驚異等意思，意為“竟會”。(六)need的用法【例句觀察】You needn't water the tomato plants now. Need he come now? Yes, he must. / No, he neednt. / he doesnt have to. 【結(jié)論1】need作情態(tài)動詞表示“需要”，“必要”。通常用于否定句、疑問句、條件句中，且只有現(xiàn)在時，其他時態(tài)用“have to”的相應(yīng)形式代替。【翻譯句子】(22) The house needs repairing.The house needs to be repaired.房子需要修理?！窘Y(jié)論2】need還可以用作行為動詞，其變化和一般的動詞相同。若主語為動作承受者時用動詞主動形式表示被動意義或用不定式的被動形式?！疽呻y1】 Must I finish my homework now? No, you needn't.【疑難剖析1】“Must？”一般疑問句的否定回答要用：No, sb. needn't.(七)dare的用法【翻譯句子】(23) She dare not go there.她不敢去那兒。(24) How dare she do such a thing?她怎敢做那樣的事情？【結(jié)論1】 dare作情態(tài)動詞表示“敢于”用于否定句、疑問句和條件句中?！痉g句子】(25) I dare say he is right.我想他大概是對的吧。They've lived here since 2020;2020.【結(jié)論2】 慣用短語“I dare say”意為“我想，大概”?！痉g句子】(26) 你敢往海里跳嗎？Do you dare to jump into the ocean?(27) 我不敢問她。I don't dare (to) ask her.【結(jié)論3】dare還可以用作行為動詞，其變化與一般動詞相同。 (在否定句中時，dare后的“to動詞原形”可以省略to)。二、情態(tài)動詞的特殊用法情態(tài)動詞除各自有自己的詞義外，還可以表示猜測和責備(虛擬)等意義。情態(tài)動詞表推測用法can / must / may / should這四個情態(tài)動詞可以用于推測，可以對現(xiàn)在狀態(tài)、現(xiàn)在正在進行的動作、過去已經(jīng)發(fā)生的動作或?qū)戆l(fā)生的動作進行推測。(一)對現(xiàn)在狀態(tài)、現(xiàn)在正在進行的動作的推測，用“情態(tài)動詞動詞原形”結(jié)構(gòu)。1. can【完成例句】(28) He is in hospital. He can't be at school.他在住院，他不可能在校學習。(29)英語課開始了，他們不可能在打網(wǎng)球。English class has begun. They can not be playing tennis now.【結(jié)論1】否定句：意為“不可能”?！就瓿衫洹?30) Can he have been to America?他會不會去過美國？【結(jié)論2】疑問句：意為“會不會”。2. may【完成例句】(31)他有輛車，他可能坐車來，但我不確定。He has a car. He may come by car, but I am not sure.(32)他們在上體育課。男孩們可能正在打球。They are having PE. Boys may be playing basketball.【結(jié)論1】肯定句：意為“也許，可能”(might 的可能性更小)【完成例句】(33)沒有人來接電話，他可能不在家。No one comes to answer the phone. He may not be at home.【結(jié)論2】否定句：意為“也許不 / 沒有，可能不 / 沒有” (注意與can't 否定猜測時意思的對比)。3. must【完成例句】(34)地面是濕的，昨天晚上肯定下過雨。The ground is wet. It must have rained last night.【結(jié)論】只能用于“肯定句”表示猜測，意為：“肯定，必定”(I am sure that)4. should, ought to【例句觀察】It's spring now. It should be warm.現(xiàn)在是春天了，應(yīng)該暖和點了。The new coat ought to be ready on Thursday.新外套到禮拜四應(yīng)該能準備好了。【結(jié)論】 肯定句 “理應(yīng)，應(yīng)當”(按常規(guī)、常理、風俗習慣等進行推測)。(二)對過去所發(fā)生的事情的推測，用“情態(tài)動詞完成式”結(jié)構(gòu)?！就瓿衫洹?35)房間里沒有燈光，他們肯定已經(jīng)上床睡覺了。There's no light in the room. They must have gone to bed.【結(jié)論1】must have done 一定做過某事。【完成例句】(36)他昨天不可能住酒店，他住在我家。He couldn't have lived in the hotel because he stayed with me in my house.【結(jié)論2】can have done / cannot have done表示對過去所發(fā)生的行為的懷疑和不肯定，通常用在否定句和疑問句中?！痉g句子】(37)你本來可以把工作做得更好一些的。You could have done the work better.【結(jié)論3】 could have done本來可以做而實際上未做。【完成例句】(38)他也許可以給你更多的幫助，盡管他很忙。He might have given you more help, even though he was very busy.【結(jié)論4】may / might have done也許 / 或許已經(jīng)；本來可能(但實際上沒有發(fā)生)；本來應(yīng)該或可以做某事(含有輕微的責備語氣)?！痉g句子】(39)你本應(yīng)該更加仔細地做這個練習。You should / ought to have done the exercise more carefully.【結(jié)論5】should / ought to have done本來應(yīng)該做而實際上未做。(有“弦外之音，言外之意”。事實上，動作在過去并未發(fā)生過。)而ought not to have done; shouldn't have done表示“本來不應(yīng)該做而實際上做了”?！就瓿衫洹?40)你本來不必來校上課，因為今天是星期天。Today is Sunday. You needn't have come to school for lessons.【結(jié)論6】needn't have done 本來沒必要做而實際上做了?！疽呻y1】You must go now, needn't you?You mustn't smoke here, must / may you?【疑難剖析1】當must作“必須”意義時，其反義部分用needn't；當含有mustn't時，其反意部分用must / may?！疽呻y2】You must be hungry now, aren't you?You must have heard about it, haven't you?You must have watched that football match last night, didn't you?【疑難剖析2】當情態(tài)動詞表推測時，反義部分的動詞形式根據(jù)情態(tài)動詞后面所隱含的時間來確定。