1、（一） 情態(tài)動(dòng)詞?？键c(diǎn)（一） 表能力如：I am starving to death。I can eat two bowls of rice now。（現(xiàn)在的能力）我快餓死了，現(xiàn)在我能吃兩碗米飯。 If you have a good sleep，you will be able to work out this problem。（將來(lái)的能力）如果你好好睡一覺(jué)，你將能夠解出這道題。 The fire spread through the hotel very quickly but everyone was able to get out。（過(guò)去有能力做并且成功的做了某事）盡管這場(chǎng)大火迅速蔓延

2、到了整個(gè)賓館，但是每個(gè)人都能夠逃出去。 I could have worked out the problem，but I didnt。（過(guò)去有能力做但未做）我本來(lái)可以解決這個(gè)問(wèn)題，但沒(méi)有解決。（二） 表推測(cè)（可能性）1. 可能性可分為客觀的可能性和具體事情實(shí)際發(fā)生的可能性兩種。所謂客觀的（理論的）可能性即并不涉及具體某事是否會(huì)發(fā)生，此種用法常?？梢哉f(shuō)明人或事物的特征。情態(tài)動(dòng)詞can可用于肯定句中表示客觀的（理論的）可能性，而表示具體事情實(shí)際發(fā)生的可能性時(shí)，can一般不用于肯定句。如：Accident can happen on such rainy days。這樣的多雨天氣有可能會(huì)發(fā)生事故。

3、（客觀的可能性）Peter may come with us tonight，but he isnt sure yet。彼得今晚可能和我們來(lái)，但他還沒(méi)確定。（實(shí)際可能性，不用can）2. 表示具體事情實(shí)際發(fā)生的可能性：（1）表示具體事情實(shí)際發(fā)生的可能性的層次比較詞形肯定式否定式疑問(wèn)式must必定，必然/will很可能，大概不會(huì)，不該會(huì)嗎？would可能性比will小語(yǔ)氣比wont弱語(yǔ)氣比will弱should說(shuō)話者有較大的試探性/ought to說(shuō)話者有較大的試探性（含義同should）/can/不可能有可能嗎？could可疑的可能不可能語(yǔ)氣比can弱may或許，也許，也未可知，也說(shuō)不定可能不

4、/might比may還弱比may not還弱/（2）表示具體事情實(shí)際發(fā)生的可能性時(shí)，may，must常用于肯定句，一般不用于否定句和疑問(wèn)句（may not表示“可能不”）；can常用于否定句、疑問(wèn)句或感嘆句中，表示疑惑、驚訝或不相信等意思；could既可用于肯定句，又可用于否定句、疑問(wèn)句中。如：This cant/ couldnt be done by him。（表不相信）這不可能是他做的。This may not be done by him。（表不確定）這可能不是他做的。He could be on his way home now。（could不如may/ might常用）他現(xiàn)在可能在回

5、家的路上。Can this be done by him？（表示疑惑、驚訝）這可能是他做的嗎？Mr. Bush is on time for everything。How can it be that he was late for the opening ceremony？（表示疑惑、驚訝）布什先生做每件事都很按時(shí)。他怎么可能在開(kāi)幕儀式上遲到呢？I didnt hear the phone。I must have been asleep。（表肯定）我沒(méi)聽(tīng)到電話。我肯定已經(jīng)睡著了。3. would，could，might并不一定與過(guò)去時(shí)間有關(guān)，而是表示可能性弱于他們相應(yīng)的現(xiàn)在時(shí)形式。另外sho

6、uld也不一定與過(guò)去時(shí)間有關(guān)。如：This may/ might be done by him。（后者比前者語(yǔ)氣弱）這件事有可能是他干的。4. should/ ought to表推測(cè)時(shí)，表示說(shuō)話者有較大的試探性。如：He ought to/ should be here on timehe started early enough。他應(yīng)該按時(shí)到這里他出發(fā)的夠早的。We should arrive before dark。我們按說(shuō)能在天黑前到達(dá)。The roads should be less crowded today。今天路上應(yīng)該不至于那么擁擠了。（三） 表請(qǐng)求、允許、允諾1. 當(dāng)對(duì)方是決策

7、者時(shí)，你代表你（們）自己（I，we）或代表第三者（he，she，they）向?qū)Ψ剑▂ou）請(qǐng)示或提出建議時(shí)用：Shall I（we）？Shall he/ she/ they？Would/ Will you？如：Shall we begin our class？Shall the driver wait outside？When shall my father be able to leave hospital？Would you do me a favor？2. could/ might/ would/ should表委婉語(yǔ)氣的功能。如：Could/ Might I use your bike

8、 tomorrow morning？Yes，you can/ may。（否定：No，Im afraid not。）不可以說(shuō)，Yes，you could/ might?；卮鹪试S時(shí)，用could/ might表委婉是不恰當(dāng)?shù)?。如：Could I borrow your dictionary？Yes，of course you can。3. 當(dāng)你自己（I）是決策者，給對(duì)方（you）或第三者（he，she，they）以命令、警告、允諾或威脅時(shí)，要用shall。此外，當(dāng)宣布法律、規(guī)定時(shí)，也要用shall。如：You shall leave the room at once，and he also sha

9、ll。（= I order you and him to leave the room at once。）你馬上給我滾出去！他也一樣。（說(shuō)話者的意志）It has been announced that candidates shall remain in their seats until all the papers have been collected。通知稱在所有試卷收上來(lái)之前，應(yīng)試者必須留在座位那里。（規(guī)則或規(guī)定）（四） 表必要性1. must常用來(lái)表示必要性，意為“必須”。表示現(xiàn)在或?qū)?lái)必須做某事用“must + 動(dòng)詞原形”；表示現(xiàn)在或?qū)?lái)不必做某事時(shí)，用dont have to

10、 do sth. 或dont need to do sth. 或neednt do sth.；表示過(guò)去沒(méi)必要做某事時(shí)，分為以下情況：當(dāng)表示過(guò)去沒(méi)必要做某事，但事實(shí)上卻做了，用neednt have done sth.；當(dāng)表示過(guò)去沒(méi)必要做某事，而不涉及是否已經(jīng)做了，可用didnt have to do sth. 或didnt need to do sth. 或It was not necessary to do sth.等。如：You neednt have worded that late last night。It was harmful to your health。你昨晚本不必工作到那么

11、晚，那對(duì)你的身體不好。Did you work very late last night？No，I didnt。I didnt need to work very late。您昨天晚上工作到很晚了嗎？不是很晚，我沒(méi)必要工作到很晚。2. should也可以表示必要性，意為“（義務(wù)上）應(yīng)該”。should表必要性時(shí)，在語(yǔ)氣上比must（必須）弱。“should + 動(dòng)詞原形”表示現(xiàn)在或?qū)?lái)應(yīng)該做某事（的必要性）；“should + have + 過(guò)去分詞”表示過(guò)去本該做某事（的必要性）。如：I should go and visit him this afternoon，but I wonder

12、if I will be free。今天下午我應(yīng)該去看望他，但我不知道我是否有空。（表示將來(lái)的必要性）You should have come to the conference yesterday。What was the reason for your absence？你昨天應(yīng)該參加那個(gè)會(huì)議。你缺席的原因的是什么？（表示過(guò)去的必要性）（五） “情態(tài)動(dòng)詞 + have done”用法一覽表（六）情態(tài)動(dòng)詞 + 完成式意義例句must have done“想必/準(zhǔn)是/一定做了某事”，否定式為cant/ couldnt have doneIt must have rained last night

13、，for the road is quite muddy。The lights were off。They must have been asleep。can/ could have done“本來(lái)能夠”“過(guò)去可能會(huì)”Can he have gone to his aunts？You could have come 5 minutes earlier。can/ could not have done“過(guò)去不可能”“過(guò)去沒(méi)能”I saw Mr. Wang just now。He couldnt have gone to Beijng。may/ might have done“也許/或許已經(jīng)”。一

14、般只用于肯定句和否定句中（在否定句中表示“可能不”），不用于疑問(wèn)句。用might則表示語(yǔ)氣更加不肯定。Its too late。I think he may have gone to bed。He may not have finished the work。She might have caught a cold。should/ ought to have done“本該做某事，而實(shí)際上未做”You should have come to the meeting earlier。You ought to have done this exercise more carefully。shoul

15、dnt/ ought not to have done“本不該做而做了某事”You shouldnt have told her the truth。neednt have done表示“做了本來(lái)不必去做的事”。注意：didnt need to do表示“沒(méi)必要做并且實(shí)際上也沒(méi)有做某事”。You neednt have 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用于事后的建議，含輕微責(zé)備的口吻

16、，意為“要是當(dāng)時(shí)做了某事就好了”，其否定式had better not have done表達(dá)相反的含義。You had better have started earlier。You had better not have scolded her。would rather have done表示“寧愿當(dāng)時(shí)做某事”，其否定式would rather not have done表達(dá)相反的含義，兩者都表示“后悔”之意。I would rather have taken his advice。I raised objections at the meeting，but now I would rat

17、her not have done that。would like/ love to have done表示過(guò)去愿意做某事，但未做成。I would love to have gone to the party last night but I had to work extra hours to finish a report。（七） 情態(tài)動(dòng)詞其他用法要點(diǎn)1. cannot but + do sth.表示“不得不，只好”。如：I cannot but choose to go。我只好去。2. may well和may as well結(jié)構(gòu)（1）“may well + 動(dòng)詞原形”是一種常用結(jié)構(gòu)，

18、意為“完全能，很可能”，相當(dāng)于to be very likely to。如：He may well be proud of his son。他大可為兒子感到自豪。Her appearance has changed so much that you may well not recognize her。她的模樣變化太大，你很可能認(rèn)不出她了。（2）“may/ might as well + 動(dòng)詞原形”意為“最好，滿可以，倒不如”，相當(dāng)于had better或to have no strong reason not to。如：You may as well do it at once。你最好馬上就

19、做這件事。You may as well stay where we are。我們留在現(xiàn)在的地方倒也不錯(cuò)。3. can not（或never）等否定詞與enough連用表示“再也不為過(guò)”。具體用法見(jiàn)形容詞、副詞專題。4. may可以用于祈使句，表示祝愿。如：May we never forget each other。愿我們彼此永不相忘。May you return in safety。愿你平安歸來(lái)。5. Why/ How + should結(jié)構(gòu)表示說(shuō)話人對(duì)某事不能理解、感到意外、驚異等，意為“竟會(huì)”。如：Why should you be so late today？你今天來(lái)的怎么這么晚？Ho

20、w should I know？我怎么會(huì)知道？（意為：我不知道。）6. must表示“偏要、硬要”做某事。如：How old are you，madam？If you must know，Im twice my sons age。夫人，您多大了？如果你硬要知道的話，我是我兒子年齡的兩倍。7. may作“可以”講時(shí)，其否定式常用“mustnt”表示“禁止”；must作“必須”講時(shí)，其否定式是“neednt”，表示“不必”。如：May I use your car？No，you mustnt。我可以使用你的車嗎？不，不行。（委婉的拒絕可用：Sorry，but I am using it now。或

21、Youd better not。等）Must I work out the problem tonight？No，you neednt。我今晚必須算出這道題嗎？不，你不必。8. need和dare的用法need和dare兩者既可用作情態(tài)動(dòng)詞也可用作行為動(dòng)詞。作行為動(dòng)詞時(shí)，有人稱和數(shù)的變化，可用于肯定句、否定句或疑問(wèn)句中，構(gòu)成否定句或疑問(wèn)句時(shí)要用助動(dòng)詞do，does，did；作情態(tài)動(dòng)詞時(shí)，沒(méi)有人稱和數(shù)的變化（dare可以有過(guò)去式dared），直接跟動(dòng)詞原形，只用于否定句和疑問(wèn)句中，構(gòu)成否定句和疑問(wèn)句時(shí)不用助動(dòng)詞。另外，dare作情態(tài)動(dòng)詞時(shí)，還可用于條件句中，過(guò)去式為dared；作行為動(dòng)詞時(shí)，da

22、re用于疑問(wèn)句或否定句，后面的to也可省略；I dare say是習(xí)慣說(shuō)法，意為“我想，大概”。如：He neednt do that。（情態(tài)動(dòng)詞）他不必那么做。He doesnt need to do it。（行為動(dòng)詞）他不必做它。I didnt know whether he dared say that to him。（情態(tài)動(dòng)詞，有時(shí)態(tài)變化）我不知道他是否敢對(duì)他說(shuō)那個(gè)。He didnt dare（to）do that。（行為動(dòng)詞）他不敢那么做。He dared not do it。（情態(tài)動(dòng)詞）他不敢做它。注意：need作行為動(dòng)詞時(shí)，還可表示“需要”，后接動(dòng)名詞的主動(dòng)形式表示被動(dòng)含義（詳見(jiàn)

23、“非謂語(yǔ)動(dòng)詞專題”）。如：The floor needs sweeping。這地需要打掃了。易錯(cuò)知識(shí)總結(jié)（一） 易混點(diǎn)歸納（一） “情態(tài)動(dòng)詞 + have done”結(jié)構(gòu)的用法區(qū)別“情態(tài)動(dòng)詞 + have done”這一考點(diǎn)，主要涉及以下幾個(gè)結(jié)構(gòu)：1. can（could）/ may（might）/ must + have done多用來(lái)對(duì)過(guò)去發(fā)生的情況作出語(yǔ)氣強(qiáng)弱不同的推測(cè)。具體使用時(shí)請(qǐng)注意以下幾點(diǎn)：（1） can表推測(cè)，一般用于疑問(wèn)句和否定句，極少用于肯定句。如：Can she have gone to school？No，she cant have gone to school。I sa

24、w her just now。（2） may表推測(cè)，一般不用于疑問(wèn)句；疑問(wèn)句中該用can，could或might。如：How could he have forgotten such an important thing？（不用may）Might you have met him somewhere？（不用may）（3） must表推測(cè)，一般不用于否定句；否定句中應(yīng)用can或could。如：誤：We mustnt have met before。正：We cant have met before。（4） 表推測(cè)時(shí)could，may，might用于肯定句語(yǔ)氣較弱；must用于肯定句語(yǔ)氣很強(qiáng)；ma

25、y，might用于否定句語(yǔ)氣較弱；can，could用于否定句語(yǔ)氣很強(qiáng)。如：He could/ may/ might have gone to school。他可能上學(xué)去了。He must have gone to school。他肯定是上學(xué)去了。He may/ might not have gone to school。他也許沒(méi)去上學(xué)。He cant/ couldnt have gone to school。他肯定沒(méi)去上學(xué)。2. should/ ought to + have done在肯定句中表示“該做的事情沒(méi)有做”，在否定句中表示“已做了不該做的事”。通常用來(lái)表示一種義務(wù)、自責(zé)或提出委婉

26、的批評(píng)。如：You should/ ought to have come here earlier。You shouldnt/ ought not to have told her the news。I should have done my homework last night，but I watched TV instead。3. neednt + have done可用來(lái)表示“已做了不必做的事”。如：There is no school today。You neednt have come。4. could + have done可用來(lái)表示沒(méi)做某事的遺憾。如：She came here

27、 on foot，but she could have come by bus。5. could/ might + have done也可用來(lái)表示委婉的批評(píng)。如：You could have come 5 minutes earlier。You might at least have written me a letter。6. 在反義疑問(wèn)句中，表推測(cè)的情態(tài)動(dòng)詞不出現(xiàn)在簡(jiǎn)短問(wèn)句部分。句中有過(guò)去時(shí)間狀語(yǔ)的，問(wèn)句部分用過(guò)去時(shí)，否則，用現(xiàn)在完成時(shí)。如：He must have been there yesterday，wasnt he？He must have been there，hasnt he？He must have been there yesterday，was he？He must have been there，has he？（二） 情態(tài)動(dòng)詞后面接進(jìn)行時(shí)的情況1. can后面接進(jìn)行時(shí)表示可能正在發(fā)生的動(dòng)作。如：What can she be doing at this moment？這個(gè)時(shí)候她會(huì)在做什么呢？You cant be telling us the truth。你不可能在對(duì)我們講真話。Can he be still thinking