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1、 1 情态动词 课标解读 1.熟悉情态动词的特征和基本用法 情态动词用于表示说话人的语气、情感和态度。用法上,情态动词后要跟动词原形。2.熟悉虚拟语气的形式,意义并能正确理解文章中出现虚拟语气的句子。考点一、情态动词的基本用法(一)can 和 could 的用法 could 是 can 的过去式,此外,could 还可以表示委婉语气 1.表示能力 eg.When she was 8 years old,she could play the piano very well.(她八岁时弹钢琴弹得很好)2.表示允许或请求允许,常用于第一人称或第二人称。eg.Can/could I use your
2、mobile phone?(请求允许)我可以用一下你的手机么?Of course,you can.(表示允许)当然可以 could 表示委婉语气,但回答要用 can,不能用 could 3.表示推测,只能在疑问句或否定句中,意思是“可能”。2 can/cant be/do“可能/不可能”推测现在的情况 can/cant be doing“可能正在/不可 能正在”can/could have done“可能做过”推测过去的情况 cant/couldnt have done“不可能做 过”eg.Its so late.Can Tom be reading?(这么晚了,汤姆还在看书么?)It can
3、t be Mary,she has fallen ill.(这个人不可能是玛丽,她生病了)I saw him just now,so he couldnt have gone abroad.(刚才我还看见他了,所以他不可能出国了)对过去的推测时,cant/couldnt 后跟 have done,意为“不可能做过某事”,couldnt 表示的可能性比 cant 小。My glasses arent here.Where can I have put them?(我的眼镜不见了,我可能把它放哪儿了呢?)4.can 表示客观上的可能性,意为“有时候会”。eg.Even an experienced
4、 teacher can make mistakes.(即使有经验的教师也可能犯错)It can be very hot in our city in summer.(在我们的城市夏天有时会很热)5.用于疑问或感叹句中,表示惊异、怀疑或不相信等态度。3 eg.How can you be so foolish!(你怎么能这么愚蠢!)How can you play a trick on me?(你怎么能捉弄我呢?)6.用于一些习惯表达中 canttoo/enough 无论都不过分;越越好 cant help but do sth 不得不做某事;只好做某事 cant help(doing)sth
5、 情不自禁做某事 区别:cant help to do sth 不能帮忙做某事 eg.She cant help to clean the house because shes busy making a cake.We cant thank you too much for what you have done for me.(对于你为我们做的一切,我们怎么感激都不过分)I cant help but admire his courage,strength and competence.(我不得不赞赏他的勇气、毅力和能力)Stop biting your nails.(别咬指甲了)I can
6、t help it.(我忍不住了)7.can 与 be able to 的区别 意义 例句 can 表示过去获得的能力,但不表示有没有做某事 Tom can sing Chinese songs.汤姆会唱汉语歌曲。be able to 表示过去有能力并且成功地做了某事,相当于 manage to do或 succeed in doing sth The fire spread quickly,but everyone was able to get out.大火蔓延得很快,但大家都成功地逃了出来。(1)can 可用于人或物做主语的句子中,但 be able to 只能由有生命 4 的名词做主语
7、。He can solve the problem./A fan can make you feel cool.(扇子可以使你感到凉爽)At last he was able to reach the top of the hill.(2)can 只有一般现在时和一般过去时,但 be able to 可用于一般现在时、一般过去时、一般将来时和完成时。He is able to swim./He was able to swim./He will be able to swim./He has been able to swim.(3)be able to 强调通过努力而获得的能力,而 can
8、强调自身具有的能力。He is able to speak English./He can speak English.(4)can/could 可表示“许可”、“允许”、“推测”,但 be able to不能这样用。You can smoke here./He can be at home.(二)must 的用法 1.表示“必须”,多用于义务、责任或强制命令,语气比 should、ought to 强,否定形式为:neednt/dont/have to mustnt 表示禁止,是 may 作“可以”讲时的否定形式 eg.May I smoke here?(我可以在这里吸烟吗?)No,you
9、mustnt.(不可以)eg.You must practise your spoken English if you want to improve.(如果你想提高,就必须练习英语口语)5 Must we hand in our exercises today?Yes,you must./No,you neednt/dont have to.(是的,必须交/不,不必交)2.must 与 have to 的区别 用法 形式的变化 例句 must“必须”,表示主观需要或责任感驱使,有必要做某事 must 没有人称、数和时态的变化,其否定形式为neednt/dont have to He said
10、 thst he must work hard.(他说他必须努力工作)Must I do it at once?(我必须立即做这件事么?)No,you neednt.(不,不必)have to“不得不”,表示由于客观条件、环境所迫而做某事 have to 有人称、数和时态的变化,其否定形式为 dont have to(现在时:have to;过去时:had to;完成时:have/has had to;将来时:will have to)My brother was ill,so I had to call the doctor in the middle of the night.(我哥哥病了
11、,所以我不得不半夜给医生打电话)You dont have to tell him about it.(你不必把此事告诉他)3.must 表推测,表示有把握的,肯定推测,只能用在肯定句中,意思是“一定”,“准是”。must be/do 对现在的动作或状态进行 推测现在的情况 肯定推测 must be doing 对现在正在进行的动作进行肯定推测 6 推测过去的情况 must have done“一定做过”注:must have done 是对过去发生的事情的有把握的肯定推测,意为“一定做过、一定发生过”用于肯定句,对应的否定推测 cant/couldnt have done 意为“不可能做过”
12、eg.You have worked hard all day.You must be tired.(推测现在的状态)你努力学了一整天,一定累了吧。He must be reading a novel now.(推测现在正在进行的动作)你现在一定在看小说。They are playing basketball,so they must have finished their homework.(推测过去的动作)他们在打篮球,所以他们一定已经完成了作业。4.表示倾向,态度,意为“偏要、偏偏”,常指做令人不愉快的事。eg.Must you shout so loudly?(你非要这么大声嚷嚷吗?)
13、If you must smoke,at least you could use an ashtray.如果你一定要吸烟,起码可以用一个烟灰缸吧。(三)may 与 might 用法 might 是 may 的过去式,常用于间接引语 1.表示请求、许可,多用于肯定句和疑问句中,might 的语气比 may更委婉。eg.May I use your telephone?(我可以用你的电话吗?)Yes,you may/can.(是的,可以)No,you mustnt/cant.(不,不可以)7 2.表示推测,用于肯定句中,意为“可能、也许”。may/might+be/do“也许”推测现在的情况 ma
14、y/might+be doing“也许正在”推测过去的情况 may/might have done“也许做过”eg.I thought you might like something to read,so I bought some books for you.(我想你可能喜欢读点东西,因此我给你买了些书)They may be still waiting for you.(他们可能还在等我们呢)They might have read about the news in the newspaper.(他们可能已经从报纸上知道这个消息了)may/might have done 还可以表示虚拟
15、,意为“本来可能做某事,但实际上没有做”。eg.He might have given you a hand,but he was too busy.(他本来可能会帮助你的,但他太忙了)3.表示祝愿,常用于祈使句中。eg.May you succeed!(祝你成功)这是一个倒装句,may 提到了主语 you 的前面。May your dream come true!(愿你梦想成真)4.may/might as well为习语,意为“不妨;还是为好”eg.We may as well stay here for another day.(我们不妨在这里再待一 8 天)may/might as w
16、ell 后接动词原形 Since its a fine day,we might as well walk.(既然天气很好,我们不妨散散步)(四)will 与 would 用法 would 是 will 的过去式,也可以表示委婉语气。1.用于各种人称,表示主语的意愿、意志、决心。eg.I will tell you all about it.(我乐意告诉你一切)He said she would help me do the housework.(她说她会帮我做家务)2.用于含有第二人称的疑问句中,表示请求、建议。eg.Will you hand me the book?(请你把那本书递给我,
17、好吗?)Will/would you please post the letter for me?(你能帮我把这封信寄出去吗?)Would you mind opening the window for me?(请你为我打开窗户,好吗?)3.表示习惯和倾向性,意为“总是、总会”。will 表示现在的习惯,would 表示过去的习惯。eg.Fish will die without water.(鱼离开水总是要死的)She would sit there for hours watching ships.(她过去总是坐在那里几个钟头看船)(五)shall 与 should 用法 1.shall
18、的用法 9(1)征求对方意见或许可,用于第一、三人称的疑问句句中。eg.Shall we go to the theatre this evening?(我们今晚去看戏好吗?)Shall she go now?(她现在可以走了吗?)Shall he fetch some water for you?(她去给你拿点水好吗?)含有第三人称的疑问句,表示请求。(2)表示许诺、警告、命令、威胁或在条约、法令、规则等文件中表示义务或规定,用于含有第二、第三人称的陈述句中。eg.You shall have my answer tomorrow.(含有第二人称的陈述句表示允诺)你明天可以得到我的答复。He
19、 shall be punished.(含有第三人称的陈述句表示警告)他应受到惩罚。All payments shall be made in cash.(含有第三人称的陈述句表示规定)所有的支付均必须使用现金。2.should 的用法(1)表示责任、义务,意为“应该”,也可表示推测,意为“按说应该”。eg.Young people should learn how to use computer.(年轻人应该学习如何使用电脑)They left at 5:30.They should get there now.(他们 5:30 离开的,现在应该已经到那儿了)(2)用于条件状语从句中,表示“
20、万一”。eg.If you should change your mind,do let me know it.(万一你改变主 1 0 意的话,一定要让我知道)(3)表示惊讶、恼怒或拒绝,意为“竟然”。eg.Why should you come so late today?(你今天为什么来得这么晚)should=ought to 是“应该”的意思。ought to 的否定形式为ought not to,可缩略为 oughtnt to。eg.I think she ought to apologize the public.(我认为她应该向公众道歉)You oughtnt to smoke s
21、o much.(你不应该吸这么多烟)(4)should have done(相当于“ought to have done”)意为“本应该做(实际上没有做)”,表示责备或惋惜,shouldnt have done(相当于“oughtnt to have done”)意为“本不应该做(实际上做了)”。eg.You should have told her the truth earlier.(你本来应该早点告诉她真相)She shouldnt have left without saying a word.(他本来不应该一句话不说就离开的)(六)need 与 dare 用法 分类 用法 例句 实义
22、动词 有人称和数的变化,可用于肯定句、否定句或疑问句中,构成否定句和疑问句时要用助动词 do、does、did。He didnt dare(to)do it.He doesnt need to do it.Do you dare to jump off the high wall?1 1 情态动词 没有人称和数的变化(dare 可以有过去式 dared),直接接动词原形,主要用于否定句和疑问句中,构成否定句和疑问句时不用助动词。He dared not do it.He neednt do it.Dare you jump off the high wall?另外,dare 作情态动词时,还可
23、用于条件句中;作实义动词时,dare用于疑问句或否定句,后面的 to 也可省略。I dare say 是习惯说法,意为“我想,大概”。(七)had better 1.表示委婉建议,意为“最好;不妨”,常缩写为:d better,没有人称和时态的变化,后接动词原形。eg.Youd better go to the hospital at once.(你最好立即去医院看病)Tom youd better go there today.(汤姆,你最好今天去那儿)2.had better 的各种句式:否定句:You had better not miss the last bus.(否定句中,注意 n
24、ot 的位置,在 had better 之后,疑问句将 had 提前)反意疑问句:Youd better not go out today,had you?(今天你最好不要外出,好吗?)否定疑问句:Hadnt you better take an unbrella?(你不认为该带一把伞么?)(八)“情态动词+had better”用法总结(可表推测,也可表虚拟)情态动词+have done 用法 例句 1 2 must have done“过去一定发生了/做了某事”(表推测),只用于肯定句中。It must have rained last night,for the road is quit
25、e muddy.昨晚一定下雨了,因为路很泥泞。can/cant have done“过去可能做了某事/过去不可能做了某事”(表推测),用在否定句和疑问句中。There is nowhere to find Tom.Where can he have gone?He cant have gone to Beijing,for I saw him just now.could/couldnt have done(1)过去可能做过/不可能做过某事(表推测)(2)过去本来能够做/没能够做(表虚拟)We couldnt have heard them because of the noise from
26、the river.(推测)If it hadnt been for your,I couldnt have succeeded.(虚拟)might have done(1)表示“也许做过某事”(表推测,把握较小)(2)表示“过去本可能做而未做”(表虚拟)It is too late.I think Tom might have gone to bed.(推测)But I think you might have told us half an hour ago.(虚拟)should/ought(not)to have done 用于肯定句中,表示“本该做某事,而实际上未做”,用在否定句中,则
27、表示“本不该做的事反而做了”(表虚拟)You are too lazy.You should/ought to have finished the work yesterday.You shouldnt/oughtnt to have told her the truth.neednt have done 表示“本来没有必要做某事而做了”(表虚拟)You neednt have taken a taxi here.(你本不必打车来这里)区别:He neednt have come.(他本来不必来)实际上来了 He didnt need to come.(他没必要来)实际上没来 (九)不同的“肯定”程度可按下列层次排列 He is at home.(事实)He must be at home.(非常肯定的推测)He could be at home.(很可能)He ought to be at home.(很可能)He may be at home.(或许)1 3 He might be at home.(或许,非常不确定)He couldnt be at home.(很可能不在家)He cant be at home.(一定不在家)He isnt at home.(事实)1 4
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