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1、共 56 页,1,专题五情态动词和虚拟语气,共 56 页,2,一、几组情态动词的区别1can 和 be able tocan 与 be able to 都可以表示能力，但两者在用法上有点差异：can(could)表示主观能力，不表示意愿或做事成功与否；be able to 表示主观意愿，强调要克服困难去做某事并成功。它的将来时用will be able to。例如：My grandma is over seventy，but she can still read without glasses.He is able to give up his bad habits.,共 56 页,3,2mu
2、st 和 have tomust 和 have to 都可以表示“必须”，但有几点区别：(1)must 强调“内在的职责”、“义务”，而 have to 强调“外界压力”、“不得已而为之”。(2)have to 可用于多种时态，而 must 一般用于现在时，其过去时与将来时分别由 had to 与 shall/will have to 代替。例如：1)You must come to the classroom before eight.2)It is raining hard outside，but I have to leave now.,共 56 页,4,(3)在回答 must 引起的问
3、题时，如果是否定的答复，不能用 mustnt，而要用 neednt 或 dont have to，因为 mustnt 是“一定不要”、“一定不能”、“禁止”的意思。例如：“Must we do it now？”“No，you neednt.”(4)must 还表示推测，语气强，常用于肯定句中，对现在发生事情的推测用must do/be;对过去事情的推测用must have done,否定式分别是cant do/be和couldnt have done.(5)must的反义疑问句用法：当句子含有时间状语的时候，根据时间状语来定助动词的时态，如:He must have been to schoo
4、l last night,didnt he?当句子不含时间状语时，根据must后面的动词来定，如：He must have been to school,hasnt he?,共 56 页,5,3used todo，be used todoing 和 be used todo(1)used todo意为“过去常常做某事”，“过去一直做某事”；be used tov.ing/n.意为“习惯于”；be used todo 意为“被用来做某事”。(2)used to 只表示过去，而 be used tov.ing/n.可表示现在、过去或将来。例如：1)He used to smoke.Now he d
5、oesnt.2)Hes quite used to hard work/working hard.3)The knife is used to cut bread.,共 56 页,6,4cant 与 mustntcant 表示“不能”，是指无能力；mustnt 表示“不能”，指的是“禁止，不允许”。在口语里，cant 也可表示“禁止，不允许”，但语气不如 mustnt 强。例如：He is so young that he cant go to school.Theres a meeting inside.You mustnt make any noise.,共 56 页,7,5can 和 m
6、ay考试中主要测试 can，may 或 could，might，表示可能性的区别及对 may 构成的疑问句的回答。(1)can，could，may，might 都可以表示可能性。can，could 表示潜在的可能性或理论上或逻辑判断上存在的可能性;而 may，might，则表示事实上的可能性。此外，can，could 还有“有能力”的意思，而may与 might 不具有此意。例如：According to the weather forecast，it may rain tomorrow.Any man with a little sense can see that he is wrong.
7、,共 56 页,8,(2)May I/we.？这一类疑问句的肯定回答为 Yes，please.或 Certainly；否定回答为 Please dont.或 No，you mustnt.例如：“May we leave now？”“No，you mustnt.You havent finished your homework yet.”6.shall用于第一、三人称时，向某人询问建议或提出意见，常用于疑问句中；用于第二、三人称时，表达允诺、威胁、警告、命令，或用于法律条文中。,共 56 页,9,7情态动词动词完成式情态动词动词完成式即“情态动词havedone”，表示对过去的行为或动作进行推测
8、、评论或判断。(1)must have donemust have done 表示对过去某事的肯定猜测。其否定或疑问形式都用 can(could)来表示。例如：Since the road is wet，it must have rained last night.He cant have missed the way.I drew him a map.,共 56 页,10,The dictionary has disappeared.Who could have taken it?当然对现在发生或将来发生的事情，要用 must do 表示猜测，否定式为 cant do。He must und
9、erstand that we mean business.You must be hungry after a long walk.,共 56 页,11,(2)may/might have donemay/might have done 表示推测过去某事“也许”发生了，may 比 might 表示的可能性在说话人看来稍大些。例如：I cant find my keys.I may/might have left them at the school yesterday.(3)could have done 在肯定句型中，往往表示委婉的批评。本可以做什么而没做；有时也用作猜测。You coul
10、d have told us earlier.Tom could have taken the dictionary.,共 56 页,12,(4)ought to/should have done和ought not to/shouldnt have doneought to/should have done和ought not to/shouldnt have done用于对已发生的情况表示“责备”、“不满”，分别表示“本应该”和“本不应该”。例如：1)With all the work finished，I should have gone to the party last night.
11、2)You ought not to have made fun of him.He is not the one you laugh at but learn from.,共 56 页,13,(5)neednt have doneneednt have done 表示过去做了某事，但没有做的必要，意为“本没必要”。例如：Yon neednt have waken me up;I dont have to go to work today.注：表示推测过去某动作发生的可能性时，就表示的可能性程度而言，must 最大，could 其次，may 更次之，might 最小。例如：I wonder h
12、ow Tom knew about your past.He must/could/may/might have heard of it from Mary.,共 56 页,14,8情态动词动词进行式情态动词行为动词进行式(即情态动词bedoing)，表示推测或评论某动作现在是否正在进行。例如：(1)He must be playing basketball in the room.(2)She may be staying at home.,共 56 页,15,二、几个情态动词使用的特定范围1表示推测时，can 不能用在肯定句中(但 could 可以)；may 和 might 不能用在疑问句
13、中。例如：Peter may come with us tonight，but he isnt very sure yet.Can it be a sunny day tomorrow?2作为情态动词，need 和 dare 不能用在肯定句中(条件状语从句除外)。肯定句中，须把它们用作实义动词，后接带 to 的不定式。例如：,共 56 页,16,【误】We need hold a meeting to discuss the matter.【正】We need to hold a meeting to discuss the matter.【正】If you need hold a meeti
14、ng to discuss the matter,Ill give you a help.3在回答由 could 和 might 引起的表示请示的一般疑问句时，不能用 could 和 might(应分别用 can 和 may)回答。例如：Could I borrow your dictionary?Yes，of course you can.,共 56 页,17,三、一些“形义不一致”的现象1过去式 could 或 might 后接动词原形可以表示对现在或将来(不是对过去)的推测。例如：Im afraid it might snow tonight.2may(not)和 cant 后接完成时态
15、，表示对过去(不是对现在或将来)的推测。例如：There were already five people in the car but they managed to take me as well.It cant have been a comfortable journey.,共 56 页,18,四、情态动词的常用形式的特殊使用1should 和 ought to 后接动词原形，常表示“应该”；但也可用来表示推测，意为“想必会”。例如：(1)Its nearly seven oclock.Jack should be here at any moment.(2)When can I co
16、me for the photos?I need them tomorrow afternoon.They should be ready by 12：00.,共 56 页,19,2could 后接完成式常表示责备语气，意为“过去本来能够，而实际上却未”。例如：We could have walked to the station；it was so near.Yes.A taxi wasnt at all necessary.,共 56 页,20,五、虚拟语气在条件句中的应用,1虚拟条件句中谓语动词的形式,共 56 页,21,(1)主句中的 should，could，might 具有情态意义
17、。(2)与将来事实相反时，条件句中谓语可由“should动词原形”构成，但要注意这里的 should 不能被 would，could，might 等替代。(3)从句中单数 be 动词的过去式一般用 were，在口语中有时也可用 was。2有时候，从句与主句所指时间并不一致，这时谓语动词应分别用其相应的形式。这时便称为错综时态虚拟条件句。例如：If he had studied hard,he would pass the exam tomorrow.,共 56 页,22,3条件句中的if省略时，从句应倒装。例如：Had they got enough boats，they would have
18、 succeeded in crossing the river.但条件句的谓语是实义动词的过去式，即谓语部分没有 had，were 或 should 时，if 不能省略，从句也不能倒装。,共 56 页,23,4含蓄条件句非真实条件有时不用条件句而用短语，或通过上下文含蓄地表达出来，但在意义上它们仍相当于条件句。例如：Without your help，we couldnt have finished it on time.要不是你帮忙，我们不可能按时完成它。But for the storm，we would have arrived earlier.要是没有暴风雨，我们还会到得早些。The
19、 ship would have sunk had it not been for the captain.要不是船长，船就沉了。Im really busy.Otherwise l would go with you.我很忙，不然我会和你去的。,共 56 页,24,六、虚拟语气在其他情况下的应用1在宾语从句中的运用(1)suggest(建议)，ask，require，demand，decide，prefer，insist(坚持要求)，command，order 等表示“建议”、“请求”、“主张”、“命令”之类的动词后接宾语从句时，从句须用虚拟语气，其形式为“should动词原形”或“动词原形
20、”。但当 suggest 作“暗示”讲，insist 作“坚持说、坚持认为”讲时不用虚拟语气。例如：All the doctors insisted that he was badly wounded and that he should be operated on at once.所有的医生都坚持认为他伤得很严重，坚决要求他立刻手术。,共 56 页,25,特别提醒：除接宾语从句外，上述动词及其相应的名词后的主语从句、表语从句亦应用虚拟语气，形式同上。例如：It is requested that Mr Wang give a performance at the party.有人请求王先生
21、在晚会上表演一个节目。(主语从句)My proposal is that we should give them more help.我的建议是我们应给予他们更多的帮助。(表语从句)He gave orders that the work be started at once.他命令立即开始工作。(同位语从句),共 56 页,26,特别提醒：idea，plan 等名词后的表语从句或同位语从句也用虚拟语气，形式同上。(2)在 wish 后的宾语从句中，须用虚拟语气，形式为：所述愿望与过去事实相反时用“had过去分词”，与现在事实相反时用过去式，与将来事实相反时用“would(不用should)动
22、词原形”。例如：I wish you had told me earlier.How I wish I were a bird!I wish someone would give me a hand.,共 56 页,27,特别提醒：wish 后接 that 从句时不能用来表示祝愿。,2在主语从句中的运用(1)在 It is necessary(important，better，natural，strange，surprising)that 这一句型中，从句的谓语动词须用虚拟语气，其形式为“should动词原形”或“动词原形”。例如：It is necessary that we should
23、make our minds without delay.,共 56 页,28,How surprising it is that he should have refused to come with you!这一句型中的形容词多是表示“重要性”、“必要性”和“合适性”的，有较强的建议、规劝和命令色彩。(2)在It is a pity(a shame，no wonder)that 这一句型中，从句的谓语动词须用虚拟语气，其形式为“should动词原形”或“动词原形”。,共 56 页,29,3在状语从句中的运用(1)as if/as though 从句若表示非真实情况可用虚拟语气，其形式为：表
24、示与过去事实相反时用“had过去分词”，与现在事实相反时用“过去式”，与将来事实相反时用“would/were going to 等动词原形”。,共 56 页,30,特别提醒：as if还可以引导表语从句。例如：He looks as if he didnt agree to that plan.as if 可以跟在 look，seem，taste，smell 等连系动词后面引导一个表语从句，从句中的谓语动词所表示的情况若可能是事实的，可用陈述语气。例如：It looks as if it is going to rain.,共 56 页,31,(2)in order that/so that
25、 引导的目的状语从句中的谓语动词一般要用虚拟语气，其形式为：表示现在情况用“may/can动词原形”，表示过去用“might/could动词原形”。(3)在 for fear that 和 in case 引导的状语从句中也常用虚拟语气，其形式为“should动词原形”。例如：She put a blanket over the baby for fear that he should catch a cold.In Britain，when people go out，they are used to taking umbrellas with them in case it should
26、rain.,共 56 页,32,特别提醒：这一句型中的 should 也可视作情态动词，意为“万一”。in case 引导的状语从句中也可用陈述语气。,共 56 页,33,4在其他情况下的运用(1)在It is(high)time that 这一结构中，定语从句的谓语动词须用虚拟语气，其形式为“过去式”或“should动词原形”。例如：It is time that we went to bed/we should go to bed.(2)当 would rather，had rather 后接省去 that 的从句时，从句中的谓语须用虚拟语气。其形式为：表示与过去事实相反时用“had过去分
27、词”；与现在或将来事实相反时用“过去式”。例如：I would rather he came tomorrow than today.我宁愿他明天来，而不是今天。这里的 would rather 和 had rather 在意义上相当于 wish。,共 56 页,34,(3)在某些表示祝愿的句子中，也常用虚拟语气，谓语动词一般由“原形动词”充当。例如：“God bless you！”said the lawyer.Long live the Peoples Republic of China!中华人民共和国万岁！(4)在 if only 引起的句子中用虚拟语气，其形式与 wish 引导的宾语从
28、句中的形式相当。例如：If only he had come in time.If only I had enough money,I could buy a car nicer than yours.,共 56 页,35,名校模拟演练,共 56 页,36,1(2010山东潍坊质量监测)The order came that the medical supplies _ to Beijing for the H1N1 flu soon.Awould be sent Bshould sendCbe sent Dmust be sent解析：考查虚拟语气。当表示愿望、请求、建议、命令等意义的动词(
29、如order,suggest,command等)后面接从句时，从句用虚拟语气，从句谓语用shoulddo,should可以省略。故选C。答案：C,共 56 页,37,2(2010安徽皖南八校二联)When shall we meet your cousin at the station?His plane took off 2 hours ago,and it _ arrive at 5 pm.Ashould BcouldCmust Dcan解析：考查情态动词的用法。should的意思是“应该会，可能”，在这里表示对将来的推测，预期会答案：A,共 56 页,38,3(2010长春调研)Has
30、Tim started?He said he would join in the party.He _.He is a man of his word.Acould have left Bmust have leftCcant come Dwont be coming解析：考查情态动词。根据“He is a man of his word”可知他是一个守信的人，因此推测他肯定已经启程了。答案：B,共 56 页,39,4(2010北京东城期末)The traffic is heavy now,so Mike _ come late.Lets wait ten more minutes.Acan
31、BneedCmay Dshall解析：考查情态动词的用法。语意：现在交通繁忙，所以Mike可能会迟到。那让我们再等10分钟吧。此处may表示“(有可能但不肯定)也许，可能”；can表示“能够”；need表示“需要”；shall用于第二、三人称的陈述句中，表示“警告、命令、威胁”等语气。据此选C项。答案：C,共 56 页,40,5(2010北京海淀期末)If you _ to my birthday party last Saturday,you would have met our old friend Jim.Oh,what a pity!Acame Bhad comeCwould come
32、 Dwould have come解析：考查虚拟语气。从语意分析，这是非真实条件句中对过去状况的虚拟，主句谓语用should/would/could/might have done，条件句用过去完成时态，答案应该选B项。答案：B,共 56 页,41,6(2010陕西西安质检)The welldressed lady was caught stealing in the fashion shop.Strangely enough,she _ have done such a thing.Awould BmustCshould Dmight解析：考查情态动词的用法。根据题干中的Strangely
33、enough可知，这里应该用should，表示惊讶，可译为“竟然”。答案：C,共 56 页,42,7(2010上海春招)It is important to know about the cultural differences that _ cause problems.Amust BdareCneed Dmay解析：考查情态动词。语意：了解一些可能会引起问题的文化差异，这很重要。此处may用来表示“可能”；must“一定，必须”；dare作情态动词常用在否定句与疑问句中，表示“敢于”；need表示“必须，需要”。根据语意，这里选D项。答案：D,共 56 页,43,8(2010临川一中)Ca
34、n I tell my best friend about it?No.Its just between you and me.You _ tell anyone else.Amustnt Bmay notCneednt Ddont have to解析：考查情态动词。根据答语的前半部分可知此处表示的是禁止，所以用mustnt。C、D两项的意思相同，表示“不必”。答案：A,共 56 页,44,9(2010河南省实验中学)Hi,Johnson,any idea where Susan is?Its class time,so she _ in the classroom now.Acan be B
35、must have beenCmight have been Dshould be解析：考查情态动词。should用于对现在比较有把握的事情的推测，符合语意。can表示可能性时多用于否定句或疑问句中。答案：D,共 56 页,45,10(2010郑州一中)Tom _ show his exam results to his parents.Adare not BdareCdare to Ddares not to解析：情态动词dare的过去式为dared，常用于否定句、疑问句及条件句中，没有人称和数的变化，其否定式是在dare后接not，再接动词原形。dare作实义动词时，有人称和数的变化，构成否定式时，其前要加助动词，后接带to或不带to的动词不定式。由此可知选A项。答案：A,
