1、专题七情态动词和虚拟语气 考点精讲 情态动词考点一情态动词的基本用法1can和could的用法(1)表示“能力”。The man can/could speak two foreign languages. 那个人能说两门外语。(2)表示推测，一般用于疑问句和否定句。Can the news be true?这个消息可能是真实的吗？It cant be true. 它不可能是真实的。(3)表示可能性。用于肯定句，常译为“往往会，常常会，有时候可能会”。Accidents can/could happen on rainy days. 车祸常会发生在雨天。(4)表示请示、允许。口语中常用coul
2、d代替can。could用以委婉地提出请求等，但回答时必须用can。Can I have a rest?我能休息一下吗？(5)cannot too/enough表示“无论也不过分”“越越好”。You cant be too careful while driving. 开车时越小心越好。You cannot remember enough English words. 你记得的英语单词越多越好。2may和might的用法(1)表示许可。might比may的语气更委婉。You may use my bike. 你可以用我的自行车。(2)表示推测，意为“可能”。may not表示一种不太确定的语气
3、，意为“可能不”。Some people who dont like to talk much are not necessarily shy; they may just be quiet people. 言语不多的人未必就是害羞；他们或许就是安静的人。(3)may表示请求时，其否定式常用mustnt表示“禁止”。May I use your car?我可以用一下你的车吗？No，you mustnt. 不行。(委婉拒绝可用：Sorry，but Im using it now. 或Youd better not. )3must(1)表示义务，意为“必须”(主观意志)。We must do ev
4、erything step by step. 我们一切都必须循序渐进地做。特别提示：回答以must开头的问句时，若是否定回答，需要用 neednt 或 dont have to。Must we hand in our exercises today?我们今天必须交练习吗？Yes，you must. /No，you neednt/you dont have to. 是的，必须交。/不，不必。(2)表示推测，意为“一定，必定”，表达十分肯定的语气，只能用于肯定句中。He must be ill. He looks so pale. 他准是病了。他脸色那么苍白。(3)表示“非得，偏要”。Must y
5、ou make so much noise?你非得弄出这么多噪声吗？4shall和should的用法(1)shall用于第二、三人称的陈述句中，表示命令、许诺、警告、强制、威胁等，此外，颁布法律、法规时也用shall。You shall have a new bike for your birthday. 你会得到一辆新自行车作为生日礼物。The new law shall come into effect next month. 新法将于下个月生效。用于第一、三人称的疑问句中，表示说话人征求对方的意见或向对方请示。Shall the man standing outside have a t
6、ry?让站在外边的那个人试试？(2)should表示义务，常译为“应该”，用于各种人称。Parents should take good care of their babies. 父母应该照顾好他们的孩子。表示惊讶、意外等，常译为“竟然，居然”。I am surprised that you should speak ill of me. 我很惊讶，你竟然说我坏话。5will和would的用法(1)表示意愿，用于各种人称的陈述句中。would常指过去的意愿。If you want to read the book，Ill give it to you. 如果你想读这本书，我可以给你。(2)表
7、示请求，用于疑问句。would语气较委婉。Will you close the window?请你关上窗户好吗？(3)表示某种倾向或习惯性动作，常译为“总是，习惯于”。would可表示过去反复发生的动作或某种倾向，后面接表示动作的动词，不能接表示状态的词。Every morning he will have a walk along the river. 每天早晨，他总是沿着小河散步。特别提示：used to表示过去的习惯动作或状态，强调现在已不存在。He would sit in the park which used to be a factory reading for hours. 他
8、过去常坐在公园里读书，一读几小时，这个公园过去曾经是一个工厂。6need和dare的用法need和dare既可用作情态动词，也可用作实义动词。用作情态动词时，主要用于否定句和疑问句。Need I come?我需要来吗？Yes，you must. 是的，你必须来。You neednt telephone him now. 你现在不必给他打电话。She dare not go out alone at night. 她晚上不敢一个人出去。考点二“情态动词have done”的用法1对过去发生的事情或状态进行推测must have done(过去)一定；语气比较肯定；用于肯定句may(might)h
9、ave done(过去)可能；语气不确定；用于肯定句和否定句can(could)have done(过去)可能，用于否定句和疑问句，表示怀疑或不确定Since nobody gave him any help，he must have done the research on his own. 既然没有人帮助他，他一定是独自做的研究。Could he have left the work unfinished?他会丢下工作不干了？2表示“与过去事实相反”could have done过去本可以做某事但实际上没做neednt have done过去本不必做某事但实际上做了ought to/sho
10、uldhave done过去本应该做某事但实际上没做oughtnt to/shouldnt have done过去本不应该做某事但实际上做了would have done过去本来想做某事而没做would not have done过去本不愿意做某事而做了The taxi driver is to blame for the serious accident. 出租车司机应为这起严重的事故负责。I cant agree more. He shouldnt have drunk. 我非常赞同。他本不应该喝酒的。(已经喝了)You neednt have watered the flowers be
11、cause it would rain soon. 你本不必浇花的，因为很快会下雨的。(已经浇了)I would have helped you but I was busy at that time. 我本来想帮你可是当时很忙。(没有帮) 虚拟语气1非真实条件句中虚拟语气的用法说明if条件句谓语主句谓语与现在事实相反动词的过去式(be的过去式通常用 were)would/should/could/might动词原形与过去事实相反had过去分词would/should/could/mighthave过去分词与将来事实相反动词的过去式(be的过去式通常用were)，should do，were
12、to动词原形would/should/could/might动词原形If I were you，I would go with him. 如果我是你，我就和他一起去。If you had studied harder last term，you could have passed the exam. 如果上学期你学习更努力的话，你考试就会及格了。If it snowed tomorrow，we would take photos. 如果明天下雪，我们就照相。特别提示：条件句中有were，had或should时，如果省略if，则需把were，had或should放在主语前，构成倒装结构。If I
13、 were in your position，I would do the same. Were I in your position，I would do the same. 假如我处在你的位置，我也会这样干的。If you had come earlier，you would have caught the bus. Had you come earlier，you would have caught the bus. 如果你来得早些，你就会赶上公共汽车了。If it should rain tomorrow，we would not go climbing. Should it rain
14、 tomorrow，we would not go climbing. 如果明天下雨的话，我们就不去爬山了。2错综时间虚拟条件句当从句谓语动词与主句谓语动词所发生的时间不一致时，它们的形式要根据各自所发生的时间作出相应的调整。If you had worked hard，you would pass the exam this time. (从句指过去，主句指现在)如果你之前努力学习的话，这次你就会通过考试了。3含蓄虚拟语气有时，假设的情况并不用条件从句表达，而是暗含在上下文中，由otherwise，but，or，without，but for 等来表达。But for your help，w
15、e couldnt have succeeded. (介词短语)要不是你的帮助，我们是不会成功的。Without electricity，life would be quite different today. (介词)如果没有电，今天的生活就会完全不同。I was ill that day. Otherwise，I would have taken part in the sports meeting. (副词)我那天病了。否则，我就参加运动会了。He telephoned to inform me of your birthday，or I would have known nothing
16、 about it. (连词)他打电话通知了我你的生日，否则，我对此一无所知。4某些从句中虚拟语气的用法(1)用于表示建议、愿望、命令等动词后的宾语从句中。常见的动词有：demand，order，require，insist，suggest，advise，request，urge，command，recommend等。宾语从句中的虚拟语气结构为“should动词原形”，should 可以省略。记忆口诀一主张：insist二命令：order，command三建议：suggest，advise，recommend四要求：request，require，ask，demand外加一个敦促：urgeTh
17、e school recommends parents not permit their children to swim in rivers or lakes during summer holidays. 学校建议父母们在暑假期间不要让自己的小孩在河里或湖里游泳。特别提示：当suggest作“暗示，表明”，insist作“坚持认为，坚持说”讲时，从句要用陈述语气。The expression on his face suggested that he was very angry. 他脸上的表情表明他很生气。He insisted (that) he heard someone in th
18、e next room. 他坚持说他听到隔壁屋里有人。(2)wish后跟宾语从句时用虚拟语气。对现在情况的假设：wish主语动词过去式(be动词通常用were)对过去情况的假设：wish主语had过去分词对将来情况的假设：wish主语would/could/might动词原形I wish (that) I were a bird and could fly freely in the sky. 我希望我是一只小鸟，能在天空自由飞翔。How I wish I had listened to my parents advice!我多么希望我听了父母的建议！I wish I could fly to
19、 the moon some day. 如果有一天我能飞到月球上就好了。(3)在“It is necessary/important/strange/natural/essentialthat从句”中，谓语动词常用“should动词原形”，should 可以省略。It is important that every member (should) know these rules. 重要的是每个成员都应该知道这些规则。It is necessary that students (should) respect teachers. 学生应该尊重老师，这是必要的。(4)would rather后跟
20、从句时用虚拟语气，表示愿望，意为“宁愿；但愿”。George is going to talk about the geography of his country，but Id rather he focused more on its culture. 乔治打算谈论他国家的地理，而我宁愿他更多地关注他国家的文化。(5)在“It is (about/high) timethat 从句”中，谓语动词常用过去式或“should动词原形(其中should不能省略)”。此句型意为“(现在)该”，用来表示建议。It is time that you went to school. 你该去上学了。It
21、is (high) time that we should start out. 我们(早)该出发了。(6)if only引导的感叹句中，用虚拟语气表示愿望。Look at the trouble were in. If only we had taken our teachers advice!瞧瞧我们所处的困境，要是我们采纳了老师的建议就好了！(7)as if，as though 引导的表语从句和方式状语从句中常用虚拟语气，与现在事实相反用一般过去时(be动词通常用were)；与过去事实相反用过去完成时；与将来事实相反，用would/could/might动词原形。It seems as
22、though it were spring already. 看起来好像已经是春天了。(事实上不是)The girl is giving us a vivid description of the moon. It seems as if she had been to the moon many times. 这个女孩对月球的描述非常逼真，就好像她去过月球很多次似的。He opens his mouth as if he would say something. 他张开嘴巴，好像要说什么。 难点释疑 难点一情态动词的易混点1can与be able to表示“经过努力设法做成某事”时不用can
23、，应用be able to can表示“能力”时，侧重于因有某种知识和技能而能办到某事。【典例】用could或was able to填空The fire spread through the hotel very quickly，but everyone_was able to get out. 解析：由句意可知此处应该是所有人经过努力最后出去了，所以应该用was able to。2表示推测的cant与may notcant表示“不可能”，may not表示“可能不，或许不”。很明显，cant比may not语气强。【典例】It _cant be the postman at the door
24、. Its only six oclock now. 解析：cant不可能，在此表示有把握的否定推测，符合句意。3cant，mustnt，neednt cant指“无能力”：mustnt指“不允许，一定不要”；neednt指“不必”：【典例】用cant，musnt或neednt填空(1)There is a meeting inside. You _mustnt make any noise. 解析：句意：里面在开会，你不许制造任何噪音。故应填mustnt。(2)He is too young and _cant make a living. 解析：句意：他太小了不能维持生计。故应填cant。
25、(3)According to todays weather report，it does not rain，so you _neednt take the umbrella. 解析：句意：根据今天的天气预报，今天不下雨，所以你没有必要带雨伞。故应填neednt。难点二对现在/将来/过去的推测情态动词可以用来对现在、将来和过去进行推测，常用来表示推测的情态动词有can/could，may/might，must，ought to/should等。1情态动词do(1)“mustdo”表示对现在的情况进行有把握的推测，一般用于肯定句，语气最强。There must be something wron
26、g. 一定出了什么差错。(2)“may/might/can/coulddo”表示对现在或将来发生的事情的推测。It might snow tomorrow or it might be merely cloudy. 明天可能下雪，或者可能只是多云。(3)“ought to/shoulddo”意为“(按道理说)应该”，表示有把握的推测，但语气上留有余地。It should be Mike who has taken away all the materials. He said he would. 应该是迈克拿走了所有的材料。他说过他要拿。2情态动词be doing“mustbe doing”表
27、示“准是正在做，一定正在做”。They must be talking about us. 他们一定正在谈论我们。 3情态动词have done表示对过去发生的事情的推测。(1)must have done意为“一定做了，准是做了，”表示非常有把握的肯定推测；cant/couldnt have done意为“不可能做了”，表示非常有把握的否定推测。(2)may/might have done意为“可能/也许做了，”表示对已经发生的事情把握较小的推测。注：“情态动词have done”的用法在前面已进行了详细解释，在此只是简单归纳。 解题策略 情态动词和虚拟语气解题“两注意”注意一：若句中谓语动
28、词为原形，在其前设纯空格题时，注意考虑情态动词。然后根据句意或句式结构填入恰当的情态动词。注意二：一旦判断所给动词在句中作谓语，就要考虑其时态、语态、语气、主谓一致等，特别是注意虚拟语气中的时态。判断虚拟语气，除了常见的if虚拟条件句，还应注意其他常搭配虚拟语气的标志词，如suggest，would rather，as if，wish，otherwise，or，but for等。【典例1】I _cant thank you enough for what you have done for me. Youre welcome. 解析：cant/can not enough表示“再也不为过”，符合句意。故填cant。【典例2】We took a taxi to the airport. Otherwise we _would have been (be) late. 解析：根据语境可知，后一句表示与过去事实相反的假设，其谓语应用would have been。 易错聚焦 1表达的单调性例如在写一封回信向好友表达建议时，重复使用You should 既显得单调，同时强硬的语气影响了交际效果。我们可以灵活多样地表达建议，如Youd better /You might as well /Why not ？等。2情态动词搭配错误