高考英语情态动词讲解修订稿

高考英语语法复习动词的分类知识讲解cry 哭泣disappear 消失go 走，趋于live 生存，居住rise 上升，增强shiver 颤抖，哆嗦sparkle 闪耀appear 出现decay 衰退exist 存在happen 发生occur 发生，出现roar 咆哮，喧闹sigh 叹息swim 游泳arise 出现，产生deteriorate 恶化fall 落下hesitate 犹豫scream 尖叫sit 坐，位于travel 旅行collapse 倒塌die 死亡flow 流动laugh 笑quiver 颤抖smile 微笑sneeze 打喷嚏lie 躺，位于，说谎age （使）成熟，变老break 打破（记录）close 关闭，结束decrease 减少，减小end 结束，终止grow 种植，生长meet 满足，对付；相遇shake 动摇，发抖spread 散布，铺开，传播stop 断绝，停止widen 加宽，变宽begin （使）开始burn 烧毁，燃烧continue （使）继续double （使）加倍finish 完成，终结improve 改善，加强open 打开，开始show 演示，说明；显示stand 忍受，抵抗；站立tear 撕毁，流泪stretch （使）伸展；使用，消耗boil （使）蒸发，沸腾change （使）改变cook 烹饪，做菜dry 弄干，变干fly 使飘扬，飞行increase 增加run 经营，运转slow 放慢，阻碍，变慢start 启动，出发turn 使旋转，转动。

届新课标高考英语精华知识点终极解密专题情态动词教案Document number【SA80SAB-SAA9SYT-SAATC-SA6UT-SA18】2013届新课标高考英语精华知识点终极解密专题04 情态动词情态动词表示说话人对动作或状态的各种观点和态度，如需要、猜测、意愿或怀疑等。

情态动词有词义，但不完全，是所谓的“辅助性”动词，在句中不能单独充当谓语。

一、情态动词的特征和形式A. 情态动词的各种形式见下表：B．情态动词除ought to, used to等外，后面只接不带to的不定式。

1．情态动词+doYou shouldn't be so careless. 你不该这样粗心大意。

Jessica told him yesterday she might not go on the trip.杰西卡昨天告诉他，她可能不去旅行了。

Difficulties can and must be overcome. 困难能够而且必须克服。

2．情态动词+be doingShe must be listening to pop music. 她肯定在听流行音乐。

You should be reviewing your lessons. 你应该在复习功课。

My mother maymight be cooking now. 我妈妈可能正在做饭。

3．情态动词+have doneThey might have visited the Great Wall. 他们可能参观过长城了。

He must have got up very early to catch the train. 他一定起得很早去赶火车了。

You ought to have come earlier. 你本该早一点儿来。

4．情态动词+be doneThis word can also be used as a verb. 这个词也可以用作动词。

情态动词和虚拟语气第一部分、情态动词一、can/could与be able to1．can/could用来表示“一般能力”；be able to有多种时态,且用来表示在特定条件下的“具体能力”.如：My grandma is over seventy,but she can still read without glasses.They will be able to tell you the news soon.He was able to flee Europe before the war broke out.2．表示允许可用can或could,与may/might意义接近.could可用于现在时,只是语气更加委婉、客气,回答时则一般要用can而不用could.—Could I have the television on?—Yes,you can./No,you can't.二、may与might1．表示允许,意为“可以,许可”,用法基本上同can与could.如：May I use your bicycle?2．表示可能性,意为“也许,可能”.如：According to the weather forecast, it may rain tomorrow.3．may可以放在句首,表示祝愿.如：May good luck be yours!三、must与have to1．must用来表示说话人的主观看法；have to表示客观的需要,强调外界压力,不得已而为之.如：He said that they must work hard.他说他们必须努力工作.(主观上要做这件事)My brother was ill, so I had to call the doctor in the middle of the night.我弟弟生病了,我只得半夜里把医生请来.(客观上需要做这件事)2．表示“不必”,须用don't have to或needn't.must的否定式表示“禁止,绝对不可”.如：You don't have to tell him about it.你不必告诉他那件事.You mustn't tell him about it.你绝不能告诉他那件事.—Must we do it now?我们必须现在做吗？—No, you needn't.不,你们不必.四、shall1．用于第一、第三人称的疑问句中,用来征求对方的意见或请求指示.如：What shall he do next?他下一步干什么呢？2．用于第二、第三人称的陈述句中,表示说话人的意愿,有“命令、警告、允诺、威胁、强制”等意思.如：He shall stay in bed.他必须躺在床上.You shall have it back next week.下周一定还你.He says he won't go, but I say he shall.他说他不去,但我说他必须去.五、will与would1．will用于各种人称,表示“意志、意愿”或“决心”等.如：If you will keep your watch half an hour slow, it is hardly surprising that you are late for your appointments.如果你想要让你的表慢半个小时,你约会时迟到就不足为怪了.2．will表示习惯性的动作,有“总是,惯于”的含义.如：An Englishman will usually show you the way in the street.英国人通常是会在街上给你指路的.3．would可表示过去反复发生的动作.如：On Sundays he would get up early and go fishing.星期天他总是早起去钓鱼.六、should与ought to1．should表示“建议”或“劝告”,有“应该”之意.如：You should learn from each other.2．ought to表示根据某种义务或必要“应当”做某事.如：Everyone ought to obey the traffic regulations.3．should和ought to也可用来表示推测,意为“想必会……”.如：—When can I come for the photos? I need them tomorrow afternoon.—They should be ready by 1200.七、情态动词表示推测1．can用于肯定句中表示客观的可能性,意为“有时会”；用于疑问句中可以表示推测,意为“可能”,有时表示一种惊讶的语气；用于否定句中也可以表示推测,can't意为“不可能”,语气很强烈.It is usually warm in my hometown in March, but it can be rather cold sometimes.我的家乡在三月份通常很暖和,但有时候也会相当冷.Mr. Bush is on time for everything. How can it be that he was late for the meeting?布什先生做什么事情都很准时,他怎么可能开会迟到呢？—Let's visit Tom together, Stephen.—There's no need to do so. He can't be at home, because I saw him board the flight to Beijing this morning.——Stephen,咱们一起拜访汤姆吧.——没必要这样做.他一定不在家,因为今天早晨我看见他登上了飞往北京的航班.2．may/might用于肯定句中可以用来表示不十分肯定的推测,意为“有可能”；用于否定句中也可以表示推测,may not意为“可能不”,表示一种不太确定的语气.The traffic is heavy these days. I might arrive a bit late, so could you save me a place?这些天交通很繁忙,我可能会来晚一点,请你帮我保留个位置好吗？3．must表示推测时只能用于肯定句中,意为“一定,必定”,表示十分肯定的语气(在疑问句中或否定句中要用can/could).—It's the office! So you must know eating is not allowed here.—Oh, sorry.——这是办公室！所以你一定知道这里不许吃东西.——噢,对不起.4．should用来表示推测时意为“应该”,即含有“按道理来说应当如此”的意思.There shouldn't be any difficulty about passing the road test since you have practiced a lotin the driving school.因为你在驾校训练了这么多,通过路考应该没什么困难.八、“情态动词＋have done”结构1．should/ought to＋have done,表示“过去本应该做而(实际)没有做的事情”,含有责备或遗憾的语气,意为“本应该……”.其否定形式为“should not/ought not to have＋done”,表示某种行为本不该发生但实际上发生了.I shouldn't have watched that movie—it'll give me horrible dreams.我本不应该看那部电影——它会令我做噩梦.You ought to have come to the party yesterday, but why didn't you come?昨天你本来应该参加聚会的,可是你为什么不来？2．must＋have done,用于肯定句,表示“过去一定做过某事”,表示一种很有把握的推测.注意,对过去发生的情况的否定推测常用“can't/couldn't＋have done”表示.—Ye Shiwen won two gold medals in London Olympic Games.—She must have gone through tough training.——叶诗文在伦敦奥运会获得了两枚金牌.——她肯定受到严格的训练.—Do you know where David is? I couldn't find him anywhere.—Well. He can't have gone far—his coat's still here.——你知道大卫在哪里吗？我到处找不到他.——大卫的上衣还在这里,因此他肯定没走远.3．needn't＋have done,表示“过去没有必要做某事,但实际上做了某事”.Mark needn't have hurried. After driving at top speed, he arrived half an hour early.马克本没必要那么匆忙.他以最快速度开车,结果早到了半个小时.4．may/might＋have done,表示对过去情况的一种不太有把握的可能性的推测,表示“可能已做了某事……”,否定句表示“可能还没有……”.Sorry, I'm late. I might have turned off the alarm clock and gone back to sleep again.对不起,我迟到了.我可能把闹钟关掉后又睡着了.5．could＋have done表示“过去本来可以做某事,但实际上没有做”；can/could＋have done表示“过去可能做了某件事”.I could have saved the poor rabbit, but I didn't have the right drugs with me at that moment.我本来可以拯救那只可怜的兔子的,可是我当时没有合适的药品.第二部分、虚拟语气一、虚拟语气在虚拟条件句中的用法1.在具体运用中,条件从句中有时可省略if而采用倒装结构.如：Had it not been for your help, we wouldn't have achieved so much.2．介词without/but for、连词but、副词otherwise常用来表示某种假设条件.如：I wouldn't have made such rapid progress without your help.3．有时候从句动作和主句动作发生的时间不一致,这时谓语动词的形式要根据各自的时间来调整.如：If the weather had been more favourable, the crops would be growing still better.二、“should＋动词原形”表示的虚拟语气这一类型常见词有“一坚持(insist)、二命令(order, command)、三建议(advise, suggest, propose)、四要求(request, require, demand, desire)”.以上词及其派生名词所接的名词性从句都使用“(should ＋)动词原形”的虚拟语气.①Jane's pale face suggested that she was ill, and her mother suggested that she(should) havea medical examination.简苍白的脸色表明她病了,她母亲建议她去检查身体.②She insisted that the man had stolen her car and that he(should) be sent to prison.她坚持说那个男人偷了她的车,并坚决要求他坐牢.三、特殊句式中的虚拟语气If only/It's (high) time (that)．..wish/would rather/as if等固定句式要求用相应的虚拟语气表达形式.①I wish I could fly.真希望我能飞.②I would rather you came tomorrow.我宁愿你明天来.③If only I had taken your advice!要是听从了你的建议该多好啊！高频考点一、考查情态动词例1．（2018·北京卷）In today’s information age, the loss of data _________ cause serious problems for a company.A. needB. shouldC. canD. must【答案】C【解析】考查情态动词.句意：在今天的信息时代,数据的丢失有时会对一个公司造成严重的问题.数据丢失造成严重问题是客观上会发生的情况,即“客观可能性”,故该空应用情态动词can.C选项正确.其余情态动词均没有该用法.need需要；should应该,竟然；must必须,肯定.【变式探究】—Can’t you stay a little longer?—It’s getting late. I reall y _____go now, My daughter is home alone.A .mayB .canC . mustD .dare【答案】C【解析】句意：——你不能再多待会儿吗?——很晚了,我必须得走了.我女儿一个人在家.A. may可能,可以,也许；B. can能,会；C. must必须,必然要,必定会；D. dare敢,胆敢.结合句意,故选C.【变式探究】________ I have a word with you? It won’t take long.A. CanB. MustC. ShallD. Should【答案】A【解析】本题考察的是情态动词基本意义辨析.Can能够,可能；must必须,一定；非得；shall将要；should应该；句意：我可以和你谈谈吗？不会花很多时间的.根据句意可知本题使用can I…？表示询问对方是否允许.如：Can I use your dictionary?我可以使用你的字典吗？故A正确.高频考点二、考查情态动词的用法例2. （2018·天津卷） I can't find my purse. I___________ it in the supermarket yesterday, but I'm not sure.A. should leaveB. must have leftC. might leaveD. could have left【答案】D【解析】考查情态动词表推测.句意：我不能找到我的钱包了,昨天我有可能把它落到超市了,但我不确定.根据句中时间状语yesterday可知,是对过去事情的推测,故用情态动词+ have done,再根据后句but I’m not sure.可知,此推测为不能肯定的推测,故用情态动词could,表示“可能”.故选D.【变式探究】（2017•天津）My room is a mess, but I __________clean it before I go out tonight.I can do it in the morning.A. daren’tB. shouldn’tC. needn’tD. mustn’t【答案】C【解析】句意：我的房间很乱,但是在今晚我出去之前不需要打扫,我可以明天早晨再打扫.A.不敢；B.不应该；C不需要；D.不许.根据句意,故选C.【变式探究】Why didn't you tell me about your trouble last week？If you ________(tell)me,I could have helped.【答案】had told【解析】句意：上个星期你为什么不告诉我你的麻烦事？如果你告诉我了,我就能帮你.根据句意和相关信息判断,条件句表示与过去事实相反的假设,此时从句用过去完成时,主句谓语用“情态动词＋have done”形式.【变式探究】I ______ have worried before I came to the new school, for my classmates here are very friendly to me.A. mightn’tB. mustn’tC. needn’tD. couldn’t【答案】C【解析】句意：我来新学校之前本没有必要担心,因为在这里我的同学对我非常友好.needn’t have done本没有必要做某事,表示实际上已经做了某事.根据句意可知选C.高频考点三、考查虚拟语气例3．(2019·天津卷)The workers were not better organized, otherwise they ________ the task in half the time.A．accomplished B．had accomplishedC．would accomplish D．would have accomplished【答案】D【解析】考查虚拟语气.句意：工人们没有被组织好,否则的话他们会用那一半的时间完成任务的.此处otherwise表达了一种含蓄虚拟；otherwise前的内容所述的是过去的事实,相当于if引导的条件状语从句“If the workers had been better organized”,因此后半部分应用“主语＋would have done sth.”的结构.故选D.【举一反三】【2018·江苏】It’s strange that he _______have taken the books without the owner’s permission.A. wouldB. shouldC. couldD. might【答案】B【解析】考查虚拟语气.句意：真奇怪,他竟然没有主人的允许就拿走了这些书.在句型”It is important/necessary/strange/impossible/natural that...”中,其中由that引导的主语从句通常用“should+动词原形”这样的虚拟语气,其中的should可以省略.故选B.【变式探究】（2017·北京）If the new safety system _______ to use, the accident would never have happened.A. had been putB. were putC. should be putD. would be put【答案】A【解析】句意：如果这个新的安全系统被投入使用过的话,这个事故就不会发生了.根据主句确定是对过去情况的虚拟,所以从句谓语用had done形式,此外根据句意可知是被动,用被动语态,故A项是正确的.【变式探究】________(have)the governments and scientists not worked together,AIDS­related deaths would not have fallen since their highest in 2005.【答案】Had【解析】句意：如果政府和科学家不共同努力,与艾滋病相关的死亡就不会从2005年的最高点下降.这是一个省略了从属连词if的虚拟语气句,使用了倒装句式.根据主句的would not have fallen可知,这里是表示过去的虚拟语气,所以用had.【变式探究】Without his wartime experiences, Hemingway____ his famous novel A Farewell to Arms.A.didn’t writeB. hadn’t writtenC. wouldn’t w riteD. wouldn’t have written【答案】D【解析】句意：没有他战时的经验,海明威就不可能写出著名的小说永别了武器.根据without his wartime experience没有战时的经历,可知表示对于过去的否定猜测,故主句用would have done,因此选D 项.1．(2019·天津卷)The workers were not better organized, otherwise they ________ the task in half the time.A．accomplished B．had accomplishedC．would accomplish D．would have accomplished【答案】D【解析】考查虚拟语气.句意：工人们没有被组织好,否则的话他们会用那一半的时间完成任务的.此处otherwise表达了一种含蓄虚拟；otherwise前的内容所述的是过去的事实,相当于if引导的条件状语从句“If the workers had been better organized”,因此后半部分应用“主语＋would have done sth.”的结构.故选D.2．(2019·江苏卷)What a pity! You missed the sightseeing, or we ________ a good time together.A．had B．will haveC．would have had D．had had【答案】C【解析】考查虚拟语气.句意：多么遗憾！你错过了这次游览.否则,我们就可以一起度过一段愉快的时光.根据关键词or可知,这里表示与过去的事实相反,谓语动词应用would/could/should/might＋have done.1.【2018·江苏】 There is a good social life in the village, and I wish I _______ a second chance to become more involved.A. hadB. will haveC. would have hadD. have had【答案】A【解析】考查虚拟语气.句意：在这个村里有很好的社交生活,并且我希望我再有机会去更多的参与.本题考查wish引导的宾语从句,表示与现在事实相反的愿望,所以从句用一般过去时.故选A.2.【2018·江苏】It’s strange that he _______have taken the books without the owner’s permission.A. wouldB. shouldC. couldD. might【答案】B【解析】考查虚拟语气.句意：真奇怪,他竟然没有主人的允许就拿走了这些书.在句型”It isimport ant/necessary/strange/impossible/natural that...”中,其中由that引导的主语从句通常用“should+动词原形”这样的虚拟语气,其中的should可以省略.故选B.3.（2018·天津卷） I can't find my purse. I___________ it in the supermarket yesterday, but I'm not sure.A. should leaveB. must have leftC. might leaveD. could have left【答案】D【解析】考查情态动词表推测.句意：我不能找到我的钱包了,昨天我有可能把它落到超市了,但我不确定.根据句中时间状语yesterday可知,是对过去事情的推测,故用情态动词+ have done,再根据后句but I’m not sure.可知,此推测为不能肯定的推测,故用情态动词could,表示“可能”.故选D.4.（2018·北京卷）In today’s information age, the loss of data _________ cause serious problems for a company.A. needB. shouldC. canD. must【答案】C【解析】考查情态动词.句意：在今天的信息时代,数据的丢失有时会对一个公司造成严重的问题.数据丢失造成严重问题是客观上会发生的情况,即“客观可能性”,故该空应用情态动词can.C选项正确.其余情态动词均没有该用法.need需要；should应该,竟然；must必须,肯定.5.（2018·北京卷）They might have found a better hotel if they _________ a few more kilometers.A. droveB. would driveC. were to driveD. had driven【答案】D【解析】考查虚拟语气.句意：如果他们多开几公里的话,他们也许会找到一个更好的旅馆.由“they might have found a better hotel”可知,该句是表示对过去的虚拟.if ____ a few more kilometers是条件句部分,表示对过去的虚拟,条件句部分要用过去完成时态,故D选项正确.1．（2017·北京）Samuel, the tallest boy in our class, ______ easily reach the books on the top shelf.A. mustB. shouldC. canD. need【答案】C【解析】A. must 必须 B. should 应该 C. can 能 D. need 需要.句意:Samuel,我班最高的男生,能很轻松地够着书架顶上的书,此处需要一个表示能力的词,故用can,答案为C.2．（2017•天津）My room is a mess, but I __________clean it before I go out tonight. I can do it in the morning.A. daren’tB. shouldn’tC. needn’tD. mustn’t【答案】C【解析】句意：我的房间很乱,但是在今晚我出去之前不需要打扫,我可以明天早晨再打扫.A.不敢；B.不应该；C不需要；D.不许.根据句意,故选C.3．（2017•江苏） _______ not for the support of the teachers, the student could not overcome her difficulty.A. It wereB. Were itC. It wasD. Was it【答案】B【解析】考查虚拟语气和倒装.虚拟语气中,be动词统一用were；虚拟语气的省略形式主要是把if省略,同时把were/should/had提前,即Were /Should/ Had I...,故选B.句意：要不是老师们的支持,该生是无法克服她自己的困难的.4．(2017·江苏卷) ____________ not for the support of the teachers, the student could not overcome her difficulty.A. It wereB. Were itC. It wasD. Was it【答案】B【解析】考查虚拟语气的省略.虚拟语气中,be动词统一用were；虚拟语气的省略形式主要是把if省略,同时把were/should/had提前,即Were /Should/ Had I...,故选B.5．（2017•江苏） _______ not for the support of the teachers, the student could not overcomeher difficulty.A. It wereB. Were itC. It wasD. Was it【答案】B【解析】考查虚拟语气和倒装.虚拟语气中,be动词统一用were；虚拟语气的省略形式主要是把if省略,同时把were/should/had提前,即Were /Should/ Had I...,故选B.句意：要不是老师们的支持,该生是无法克服她自己的困难的.6．（2017·北京）If the new safety system _______ to use, the accident would never have happened.A. had been putB. were putC. should be putD. would be put【答案】A【解析】句意：如果这个新的安全系统被投入使用过的话,这个事故就不会发生了.根据主句确定是对过去情况的虚拟,所以从句谓语用had done形式,此外根据句意可知是被动,用被动语态,故A项是正确的.1．(2016·浙江,15)________(have)the governments and scientists not worked together,AIDS­related deaths would not have fallen since their highest in 2005.【答案】Had【解析】句意：如果政府和科学家不共同努力,与艾滋病相关的死亡就不会从2005年的最高点下降.这是一个省略了从属连词if的虚拟语气句,使用了倒装句式.根据主句的would not have fallen可知,这里是表示过去的虚拟语气,所以用had.2．(2016·浙江,17)George can't ________(go)too far.His coffee is still warm.【答案】have gone【解析】句意：乔治不可能走得太远了.他的咖啡仍然是温的.can't have done是对过去的否定推测.3．(2016·北京,34)Why didn't you tell me about your trouble last week？If you ________(tell)me,I could have helped.【答案】had told【解析】句意：上个星期你为什么不告诉我你的麻烦事？如果你告诉我了,我就能帮你.根据句意和相关信息判断,条件句表示与过去事实相反的假设,此时从句用过去完成时,主句谓语用“情态动词＋have done”形式.。

【高中英语】高考英语语法复习讲解：情态动词英语语法讲解高考英语语法复习讲解：情态动词英语语法讲解”，希望能给您带来帮助。

本文题目：高考英语语法复习讲解：情态动词英语语法讲解根据以往英语取得高分同学的经验和海文英语辅导名师的建议，他们都一致认为英语语法和词汇是学好、考好英语的重要基础，其实完形填空是对语法、词汇的综合考查，但更关键的是学好此部分有助于对英语句子结构的分析和理解，有助于学生掌握灵活多变的句式，这样不仅有助于学生做好阅读理解，而且有助于学生做好英译汉，写好作文。

因此，我们在此编写了有关重点语法的知识点，并将陆续登出，同时将刊登一些试题。

希望同学们认真掌握，切不可因不靠它们而忽视了对英语基础知识的掌握。

(一)情态动词一.情态动词的现在完成式的用法情态动词现在完成式主要有两个功能：表示已经发生的情况和表示虚拟语气。

在这两个方面must/mustn’t,;can/cann’t;need/needn’t;may/mayn’t;might/mightn’t;should/sh ouldn’t;ougtht等情态动词+完成式表示的意思是有一定区别的1.表示已经发生的情况。

1)must have+过去分词，表示对已发生情况的肯定推测，译为“(昨天)一定……”。

如：My pain apparent the moment I walked into the room, for the first man Imet asked sympathetically:” Are you feeling all right?”[A] must be [B] had been [C] must have been [D] had to be(答案为C)2)can’t / couldn’t have+过去分词，表示对已发生情况的否定推测，译为“(昨天)一定没……”。

如：Mary my letter; otherwise she would have replied before now.[A] couldn’t have received [B] ought to have received[C] has received [D] shouldn’t have received(答案为A)3)may / might have +过去分词，表示对已发生的事情做不肯定、可能性很小的推测，或事实上根本没发生，译为“也许……”。

【英语】高考英语情态动词解析版汇编含解析一、单项选择情态动词1．One of our rules is that every student _______ wear school uniform while at school. A．might B．couldC．shall D．will【答案】C【解析】【详解】考查情态动词辨析。

句意：我们其中一条规则要求每个学生在校期间都要穿校服。

shall可以表示“命令，警告，强制要求；允诺；法律，规定要做……”，结合句意可知C正确。

2．Frankly speaking, I am not sure whether I ________ this in the old days with that kind of equipment, which looks quite odd and ridiculous.A．should have done B．need have done C．would have done D．must have done 【答案】C【解析】【详解】考查情态动词+have done。

句意：坦率地说，我不确定在过去我是否会用这种设备做这件事，这看起来很奇怪和可笑。

A. should have done表示本应该做某事，而实际上没有做某事；B. need have done表示本来需要做某事而没有做；C. would have done虚拟语气，表示对过去事情的假设，意思是“本来会做”；D. must have done表示对过去事情的肯定推测，译成“一定做过某事”。

由“in the old days”可知，本句表示对过去事情的假设。

故选C项。

3．—It’s already 11 o’clock , and he ______ have been here half an hour ago.—Maybe he got caught in the rain.A．must B．ought toC．may D．can【答案】B【解析】【详解】考查情态动词。

高考英语语法复习情态动词与虚拟语气知识讲解一、情态动词（1）表示能力时，can只用于一般现在时，could仅用于一般过去时；而be able to则有更多的时态，如将来时、完成时等。

I haven’t been able to read that report yet.He will be able to skate as well as you.（2）Was/were able to表示能力时，侧重经过努力而成功做到某事；而could仅表示具备能力，不说明是否实施了能力。

He studied hard and was able to pass the exam.（3）用在其他动词，如might,may,would,want,hope等之后表示能力只能用be able to。

He might be able to fix your car.（1）must还可以表示质问或感情色彩，意为“偏要，偏偏”。

Why must it snow on Saturday?（2）should还可以表示惊奇、愤怒、失望等特殊情感，尤其用在以why,who,how等开头的疑问句中或某些感叹句中。

why should you be so late today?（1）must作“必须”讲的一般疑问句，其肯定回答用must，否定回答用needn’t或don’t have to。

-Must I pay now?-Yes, you must./No, you needn’t.（2）need还可以作实义动词，有人称和数的变化，后跟带to的不定式作宾语。

She needed to go out for a walk.（1）两者在表示过去的习惯动作或行为时常可通用。

When we were children, we would/used to go skating every winter.（2）Used to与would都不能与表示具体频率、次数的词及特定的时间状语或具体的一段时间连用。