1、m sorry I cant help you. 对不起,我帮不上你。基本助动词与情态助动词最主要的区别之一是,基本助动词本身没有词义,而情态助动词则有自己 的词义,能表示说话人对有关动作或状态的看法,或表示主观设想:What have you been doing since? (构成完成进行体,本身无词义)I am afraid I must be going. (一定要)You may have read some account of the matter. (或许已经) 除此之外,情态助动词还有如下词法和句法特征:1 ) 除 ought 和 used 以外,其他情态动词后面只能接不带
2、 to 的不定式。如果我们把 ought to 和 u sed to 看做是固定词组的话,那么,所有情态动词无一例外地只能接不带 to 的不定式:We used to grow beautiful roses.I asked if he would come and repair my television set.2) 情态助动词在限定动词词组总是位居第一:They need not have been punished so severely.3) 情态助动词用于第三人称单数现在时的时候,没有词形变化,即其词尾无 -s 形式:She dare not say what she thinks
3、.4) 情态动词没有非限定形式,即没有不定式和分词形式,也没有相应的动名词:Still, she neednt have run away.5) 情态助动词的 “时 ”的形式并不是时间区别的主要标志。在不少场合,情态助动词的现在时和过 去时形式都可以表示现在、过去或将来时间:Would you mind very much if I ask you to do something?She told him he ought not to have done it.6 ) 情态助动词之间是相互排斥的,即在一个限定动词词组中只能出现一个情态助动词,但有时却 可以与 have 和 be 基本助动词连
4、用:You should have washed the wound.Well, you shouldnt be reading a novel. 用法首先它是动词,而且不同于行为动词,行为动词表示的是可以通过行为来表达的动作(如写,读, 跑),而情态动词只是表达的一种想法(如能,也许,敢)。用法是:情态动词 + 行为动词原形例句: I can read this sentence in English. 我能用英语读这句话。情态动词是一种本身有一定的词义 ,表示说话人的情绪 ,态度或语气的动词 ,但不能单独作谓语 , 只能和其他动词原形构成谓语。We can be there on time
5、 tomorrow. 我们明天能按时去那儿。May I have your name? 我能知道你的名字吗?Shall we begin now? 我们现在就开始吗?You must obey the school rules. 你必须遵守校规。情态动词数量不多 ,但用途广泛 , 主要有下列 :can (could), may (might), must, need, ought to, dare (dared), shall (should), will (would),h ave (to) ,had better.功能助动词 (auxiliary) 主要有两类:基本助动词 (primary
6、 auxiliary) 和情态助动词 (modal auxiliary) 。基本 助动词有三个: do, have 和 be ;情态助动词有十三个: may, might; can, could; will, would; shall,should; must, need, dare, used to, ought to. 上述两类助动词的共同特征是,在协助主动词构成限 定动词词组时,具有作用词的功能:1)构成否定式:He didnt go and neither did she.The meeting might not start until 5 oclock. 2)构成疑问式或附加疑问式
7、:Must you leave right now?You have been learning French for 5 years, havent you? 3)构成修辞倒装:Nowhere can he obtain any information about his sister. Hardly had he arrived when she started complaining. 4)代替限定动词词组:A: Who can solvethis crossword puzzle?B: Tom can. Shall I write tohim? Yes, do.情态动词的用法要点can
8、 和couldcan/could用法例句表示能力(体力、知识、技 能)(表示过去有能力用 could)1“I dont think Mike can type. ”2I can speak fluent English now , but I couldn t last year.3Can you lift this heavy box? (体力)4 Mary can speak three languages.(知识)5Can you skate?(技能)6.Two eyes can see more than one. 两只眼比一只眼看得清。7.Could the girl read be
9、fore she went to school? 这女孩上学前能识字 吗?在肯定句中,表示客观可能 性,(客观原因形成的能力) 。 并不涉及具体某事会发生, 常用来说明人或事物的特 征。要表达具体某事实际发 生的可能性时,不用 can,需 用 could, may, might 。1 As a human being, anyone can make a mistake.2 Im confident that a solution can be found.3 He can be very forgetful sometimes.4 I may stay at home this weeken
10、d. (实际可能性)5 Peter might come to join us.( 实际可能性 )6 It will be sunny in the daytime ,but it could rain tonight.( 实际可能性 )7 7.They ve changed the timetable, so we can go by bus instead.8 8.This hall can hold 500 people at least.9 The temperature can fall to 60, that is 60 below freezing. 气温可降至60,也就是零下
11、60。10 11.He can t (couldn t) have enough money for a new car. 他不可能有足够的钱买新车。11 12 You mustn t smoke while you re walking around in the wood.You could start a fire. (实际可能性)12 在林子里走时勿吸烟,那样可能会引起火灾。表示请求和允许。 表示请求, 口语中常用 could 代替 can, 使语气更委婉。用 can 和 may 来回答, 不能 用 could 或 might 。1.Can we turn the air condit
12、ioner on?2.Any police officer can insist on seeing a driver s license.3.In soccer, you cant touch the ball with your hands.4.Could you have her call me back when she gets home, please?5.I wonder if I could just ask you to sign this.6. Could I borrow your dictionary?-Yes, of course, you can.No, Im af
13、raid not/No,you cann t/No,you may not.表示对现在的动作或状态进 行主观的猜测,主要用在否 定句和疑问句中。1 It can t be easy caring for a man and a child who are not your own. 2 Can the man over there be our head master?3.If Tom didnt leave here until five oclock, he cant be home yet. 如果汤 姆五点才离开这儿,他此时一定还未到家。表示惊异、怀疑、不相信等 态度,主要用在否定句、疑
14、 问句和感叹句中。1 Can this be an excuse for not giving them help?2 This can t be true.3 How can you be so crazy.4 4.Can this be true?5 5.How can you be so careless!6 6.This cannot be done by him.7 Where can (could) they have gone to? 他们会去哪儿了呢?8 He can t (couldn t) be over sixty. 他不可能超过六十岁。9 How can you be
15、so careless? 你怎么这么粗心?10特别说明:(1)could 用来表示请求时,语气委婉,主要用于疑问句,不能用于肯定句,答语应用can(即: could 不能用于现在时态的简略答语中) 。如: Could I use your dictionary? Yes, you can.(否定回答可用:No, I m afraid not.)此时可与 may 互换。在疑问句中还可用could,might 代替,不是过去式,只是语气更委婉,不能用于肯定句和答语中。 Could I come to see you tomorrow? Yes, you can. ( No, I m afraid
16、not. )(2) can 和 be able to 辨析 can(could)和 be able to 都可以表示能力,意思上没有区别。但 can只有现在式和过去式,而 be able to 则有更多的形式。I ve always wanted to able to speak fluent English.Those bags look really heavy, are you sure you ll be able to carry them on your own? 但是,表示在过去某时的某一场合经过一番努力,终于做成了某事,通常不用 could ,而用 was/were ablet
17、o 来表示。 could :有潜能,但并未做到这时, was/were able to 相当于 managed to do 或 succeed in doing 。After the accident it was a long time before she was able to walk again.The fire was very big, but most people were able to escape from the building.I can sing many English songs. 我会唱许多英文歌曲。We were able to return to ou
18、r campsite before the heavy rain. 我们在下大雨前设法会到了野营地。He was able to swim across the river and escaped being caught. 他游到了河对岸,没有被抓住。 在否定句中, can/could 与 be able to 几乎没有什么差别,两者可以互换。例如:She wasn t able to/couldn t cook Fren她ch不 d会ish做es法. 国菜。(3) 惯用形式“ cannot too”表示“无论怎么也不(过分) ”。You cannot be too careful. 你越小
19、心越好。惯用形式“ cannot but+ 不定式(不带 to)”表示“不得不,只好” 。 I cannot but admire her determination. 我不得不钦佩你的决心。二 may 和 mightmust 和 have to表示“必须, 应该, 一定” 之意, 语气比 should,1You must come to school on time.ought to 强烈。其否定形式 mustnt 表示“不准,2Everybody must obey the law.不应该,禁止”等意 .3You mustn t drive so fast in the street.4W
20、e mustnt waste any more time.5I must finish my work today.must6Must I return the book tomorrow?77.The play is not interesting. I really must gonow.在回答带有 must 的问句时,否定回答常用 neednt Must I come back before ten?或 dont have to ,表示“不必” ,而不用 mustnt. Yes, you must.(No, you needn t)2.Must we hand in our exerci
21、se books today? Yes, you must. (No, you don t have to.)表示有把握的推测,意为“一定、准是、想必” ,This must be your pen.You must be hungry after a walk.只用于肯定句中。它的否定或疑问式用 can 代替 mustThere must be a hole in the wall.You re Tom s good friend, so you must knowwhat he likes best.5.Your mother must be waiting for you now.He
22、must be staying there.他现在肯定呆在那里。试比较和第一种用法的区别He must stay there. 他必须呆在那。have to8“必须,不得不”,意义与 must 相近。但 mustThe film is not interesting. I really must go也可拼做表示的是说话人的主观看法, 而 have to则往have got to。往强调客观需要 ,有被动接受的意思。无疑问11I have to go now, because my mother is in句形式,疑问句用 must 代替。hospital.912My brother was
23、very ill, so I had to callthe doctor in the middle of the night. 我弟弟病 得很厉害,我只得半夜里把医生请来。 (客观上需要做这件事 )134. Must I clean all the room?145. I must go over the test paper again tosee if there are any mistakes.我必须再检查一遍试卷看看是否有错误。156. The teacher said that there were manymistakes in my test paper, so I had
24、to go over it again.老师说我试卷中有很多错误,所以我只 好再检查一遍。16must 只有一种形式, 即现在式与过去式187. I had to work hard when I was your都是一种形式, 在间接引语中 must 可用于表age.示过去时间 .而 have to 则涉及各种人称、时 态等方面的变化形式。1719 8. I will have to learn how to use acomputer.20 9 In order to take the exam, we ll have tofinish the whole book by the end
25、of this month .21 10. told her that she must give upsmoking. 我叫她必须戒烟。22两者的否定意义不同, mustn t 表示“禁止,不许”, don t have to 表示不必。1 You mustn t go there. 2 You don t have to go there.四 shall 和 shouldshall用于第一,三人称构成的疑问句,表示征求对方意见或请求指示1 Shall I open the window?2 Shall we say 6 oclock, then?3 What shall I get for
26、 dinner?4.Shall we begin our lesson?4 5.W hen shall he be able to leave the hospital?5 Shall the boy wait outside? 让那男孩在外面等 吗?用于第二、三人称陈述句中,表示说话人给对 方的命令、警告、决心、允诺或威胁。1 Don t worry, you shall get the answer this afternoon.(允诺 )2 He shall be sorry for it one day, I tell you. (警 告)3 You shall do as I say
27、. (命令 )4 If you children don t do as I tell you, you shallnot go to the party. ( 威胁 )5 5. You shall fail if you don t警 w告ork) har6 6. He shall have the book when I finish it.( 允诺 ) 7 7. He shall be punished.( 威胁 )8 8.You shall do as I say. 按我说的做。 (命令)9 9.You shall have my answer tomorrow. 你明天 可以得到我的答复。 (允诺)10 10.He shall be sorry for it one day, I tellyou. 有一天他会后悔的,我告诉你。 (警告)11 11.Nothing shall stop us from carrying outthe plan. 什么也不能阻止我们执行这项计划。 (决心)should表示劝告或建议,
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