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情态动词高中知识点高三情态动词是一类具有特殊意义和用法的动词，它们在句子中一般与实义动词连用，表示说话人的推测、命令、请求、建议等情态。
在高中英语学习中，掌握情态动词的正确用法至关重要。
本文将介绍情态动词的相关知识点，帮助高三学生更好地运用这一语法现象。
一、情态动词的定义情态动词，又称情态助动词，是用来表示说话人对某种动作或状态的态度、推测、可能性、能力、意愿、义务等情态的一类特殊动词。
常见的情态动词包括can、could、may、might、must、shall、should、will、would等。
二、情态动词的用法1. 表示能力情态动词can表示某人具有能力或可能做某事，could用于过去说法。
例如：- She can speak three languages fluently.（她能说流利的三种语言）- He could lift the heavy boxes when he was younger.（他年轻时能搬起这些沉重的箱子）2. 表示推测和可能性情态动词may、might、could用于表示推测和可能性。
may用于表示较为肯定的推测，might和could表示推测的可能性较小。
例如：- The weather is cloudy, it may rain later.（天气多云，可能会下雨）- He might be late for the meeting.（他可能会迟到会议）3. 表示义务和建议情态动词must表示说话人对某种行为具有强烈的责任感或坚决要求，should表示建议。
例如：- We must obey the laws of the country.（我们必须遵守国家的法律）- You should apologize to your friend for your mistake.（你应该为你的错误向朋友道歉）4. 表示许可和请求情态动词can、may、could用于表示允许和请求。
情态动词情态动词有can/could/may/might/must/haveto/shall/should/will/would/oughtto/need/dar e等。
情态动词没有人称和数的变化，有词义，但不完整，不能独立作谓语，必须和不带to的动词不定式连用。
1、can与could①can与could表示能力eg:Hecanswim,butIcan't.②can与could表示客观的可能性eg:Kunmingiscalled“SpringCity”,butitcansnowinwinter.③can与could表示请求时，使用could比can语气更委婉客气，此时could和can没有时间上的差别，它主要用于疑问句，不用于肯定句，因此回答时要改用can.eg:---Could Icomehereagaintomorrow?---Yes,you can./No,I'mafraidnot.2、注意几组使用情态动词的提问和回答eg:MayIwatchTVnow?---Yes,youmay./Yes,please.---No,youmustn't./No,you'dbetternot.MustIdoitatonce?---Yes,youmust.---No,youneedn't./No,youdon'thaveto.NeedIcome?---Yes,youmust.---No,youneedn't.3、can和may表示许可时，can侧重客观情况的“许可”may侧重说话人主观上给予的“许可”。
eg:Youcansmokenow,asGrandmotherisn'there.Youmaysmokehere.4、may用于祈使句中，表示祝愿eg:Mayyousucceed!5、will的用法①主语是人时，表示意愿eg:Iwillneverdoitagain.②主语是物时，表示功能eg:Thewatchwon'twork./Thewindowwon'topen.6、shall的用法①与第一、第三人称连用的问句中，表示说话人征求对方的意见或请求。
情态动词知识点总结高中情态动词是英语中一个重要的语法现象，它们能够表达说话者的情感、态度、意愿等，以及表达说话者对事件的推测、猜测、可能性等。
了解情态动词的用法，能够帮助我们更准确地表达自己的意思，也有助于我们理解他人的意图。
本文将对情态动词的概念、用法、以及常见的情态动词进行总结和归纳，以便于读者更深入地理解情态动词的使用。
一、情态动词的概念情态动词（Modal Verb）是一类特殊的助动词，用来表示说话者的情感、态度、意愿等，以及表达说话者对事件的推测、猜测、可能性等。
情态动词通常用于句子的前面，后面跟动词原形，用来构成不同的语法结构和表达不同的含义。
英语中常见的情态动词有can、could、may、might、must、shall、should、will、would、ought to等。
这些情态动词具有一些共同的特点，比如不能独立完成谓语，后面必须跟动词原形；在疑问句和否定句中，情态动词的位置要发生变化等。
二、情态动词的用法1. 表示能力和可能性can与could表示说话者的能力或者对某种事情的可能性，其中can用于现在时，could用于过去时。
比如：I can speak Spanish.（我会说西班牙语。
）She could swim when she was five.（她五岁的时候就会游泳。
）may与might也表示可能性，may 用于现在时，might 用于过去时。
比如：It may rain tomorrow.（明天可能会下雨。
）I thought she might come.（我以为她可能会来。
）2. 表示请求和建议will与would可以表示请求，will用于肯定句，would用于否定句和疑问句。
比如：Will you please help me?（你能帮帮我吗？）I would like to go with you.（我想和你一起去。
）shall与should也可以表示请求或者建议，should更多地表示建议。
高中英语知识点归纳情态动词的用法与义项情态动词是英语中一个重要的语法现象，是一种特殊的动词形式，用来表示说话人的态度、意愿、可能性、能力、推断等。
情态动词一般不能单独使用，而是与其他动词连用，构成动词词组来表示各种意义。
下面是对高中英语知识点归纳情态动词的用法与义项的总结。
一、情态动词的意义划分：1. 可能性（Possibility）情态动词：may, might, could, can用法：- may, might, could用于表示事情有可能发生或存在；- can主要用于表示某人具备某种能力。
示例：- It may rain tomorrow. (明天可能会下雨)- He might be at home. (他可能在家)- The key could be in the drawer. (钥匙可能在抽屉里)- I can speak Spanish. (我会说西班牙语)2. 动作愿望（Desire）情态动词：would like, want, wish用法：- would like用于表示客气地提出请求或愿望；- want用于表示强烈的需求或欲望；- wish用于表示遗憾或对现在情况的不满或希望。
示例：- I would like to have a cup of coffee. (我想来一杯咖啡)- She wants to go shopping. (她想去购物)- I wish I had more free time. (我希望我有更多的空闲时间) 3. 推测与推断（Speculation）情态动词：must, may, might用法：- must用于表示说话人根据某种依据做出肯定的推测； - may, might用于表示可能性的推测。
示例：- It must be raining outside. (外面肯定在下雨)- He may/might be busy right now. (他可能正忙)4. 动作能力（Ability）情态动词：can, could用法：- can表示某人具备某种能力；- could表示过去的能力或给予请求、许可的非正式方式。
高中英语语法专题情态动词与常考短语高中英语语法专题情态动词与常考短语情态动词是许多同学在英语语法中最简单丢分的一块。
情态动词的用法很简单,情态动词都有各自的含义和搭配,如何学好英语?我在这里整理了相关资料，快来学习学习吧!高中英语语法专题情态动词一、can和could1、can的用法(1)表示体力和脑力方面的力量。
(2)表示对现在的动作或状态进行主观的猜想，主要用在否定句和疑问句中。
(3)表示可能性，理论上的可能性，意为“有时候可能会”，可用于确定句。
(4)表示允许，意思与may接近。
(5)表示说话人的推想、怀疑、惊异、猜想或不愿定等，主要用于否定句、疑问句或感叹句中。
(6)can的特别句型cannottoo / enough表示“无论怎么。
也不过分”。
“越。
越好”。
cannot but+ do sth.表示“不得不，只好”。
2、could的用法(1)表示力量，指的是过去时间。
(2)表示允许，指的是过去时间。
(3)表示可能，可以指过去时间，也可以指现在时间，表示语气缓和。
(4)委婉客气地提出问题或陈述看法，指的是现在时间。
主要用于疑问句，回答时用can。
3、can与could的区分can表推想时只用于否定句和疑问句(could无此限制)。
couldnt 的可能性比cant小。
4、can与be able to的区分(1)现在时：无区分，但后者不常用。
(2)完成时;can没有完成时，此时要用have(has,had)been able to。
(3)将来时：can没有将来时，要用will be able to。
(4)过去时：could表示一般力量，was/were able to 表示在详细场合通过努力胜利做成某事的力量。
二、may 和might1、may的用法(1)表示询问或说明一件事可不行以做。
(2)表示一件事或许会发生或某种状况可能会存在，通常用在确定句和否定句中。
留意：表示可能性时，cant语气强，表示“不行能”，may not 语气弱，表示“可能不”。
高中英语语法讲解情态动词概述1. 共有10个情态动词：can/could, may/might, will/would, shall, should, ought to, must；2个半情态动词need,dare2. 特点：（1）情态动词后加动词原形（即不带to的不定式）一起构成谓语；（2）没有人称和数的变化；（3）多数情态动词有过去式，但其过去式有时并不表示时态，而只起“委婉或不确定语气”的作用。
Would you do me a favour?She may/might be watering the flowers now.3. 情态动词在句子中可发挥不同作用，如表能力，表责任与义务，表推测，表征求允许，表请求，表建议，表语气态度等等● He can/could run 100 meters in 11 seconds.● You should/ought to/must work hard to win a gold medal.● Can/Could/May/Might I watch the Olympics tonight?● Will/Can/Could/Would you help me with my training?● He might/may/could/should/ought to/will/must watch the football match tonight.● I suggest that you should watch the opening ceremony.● Can this be true?4. (1)情态动词+do 表对一般现在或将来情况的推测(2)情态动词+ be doing 表对正在发生的事情的推测(3)情态动词+have done 表对过去已经发生的事情的推测● 常见“情态动词+have done”归纳1. could have done 过去本有能力做某事但没做（虚拟）2. may/might have done ①过去可能已经做了某事（推测）②过去本可能做某事但没做（虚拟）(责备)3. must have done过去一定已经做了某事（推测）4. can't/couldn't have done过去不可能已经做了某事（推测）5. should/ ought to have done ①过去应该已经做了某事（推测）②过去本应该做某事但没做（虚拟）（责备）6. shouldn't/ oughtn't to have done 过去本不应该做某事但做了（虚拟）（责备）7. needn't have done 过去本不必做某事但做了（虚拟）例句1) You could have got a full mark, but you were to careless.2) She may have missed the first train in the morning.3) You may have hurt yourself when climbing the tree.4) You must have stayed up late last night.5) It can't/couldn't have rained last night, for the streets are dry.6) They should have arrived in Beijing by this time.7) You should have e to the meeting earlier.8) You shouldn't have told Mary the sad truth.9) You needn't have taken a taxi here, for it was near my house.一、can/could 的用法3. 固定用法：(1) can not/never…too/enough “再怎么…也不过分，越…越好”● I can never thank you enough.● You can't be too careful.● You can never remember too many words.(2) can't + 比较级“不能更...，非常...”● I can't agree more.● The film couldn't be more boring(3) cannot but do sth. 不得不，只好● I cannot but admire your bravery.(4) can't help doing sth 情不自禁做； can't help (to) do sth 不能帮忙做二、may/might的用法3．may表示祝愿或希望。
情态动词总结I 情态动词的特征：1.本身有词义。
2.不能独立作谓语。
2. 后接动词原形一起构成谓语。
3. 不随人称和数的变化。
II 情态动词各自的基本意义及用法：1.大多数情态动词（除表‘能力、许可、意志’外），都可以表示推测，其程度有差异。
按可能性程度的高低排列为：must﹥will ﹥would ﹥ought to ﹥should完全肯定完全可能很可能﹥can ﹥could﹥may ﹥might可能有可能2. 区分情态动词的否定含义：may not或许不、可能不might not可能不can’t 不可能mustn’t不许、禁止shouldn’t不应该needn’t 不必1.情态动词表推测的反意疑问句，简单来说，就是以情态动词后的时态为淮，如句子里有明确的时间状语，则以其为准。
2.以must 为例：E.g. 1. You must be hungry now, aren’t you?2. He must be watching TV , isn’t he ?3 Tom must have lived her for a long time, hasn’t he ?4. She must have arrived yesterday, didn’t she?注：如选择题中（以She must have arrived yesterday, didn’t she？为例）既有didn’t she又有hasn’t she则以didn’t she？为最佳答案。
IV 情态动词专项练习与解析一( ) 1. You _____ return the book now. You can keep it till next week if you like.A. can’tB. mustn’tC. needn’tD. may not( ) 2. Where is my pen? I _____ it.A. might loseB. would have lostC. should have lostD. must have lost( ) 3. I wish I _____ you yesterday.A. seenB. did seeC. had seenD. were to see( ) 4. I didn’t hear the phone. I _____ asleep.A. must beB. must have beenC. should beD. should have been( ) 5. If my lawyer _____ here last Saturday, he _____ me from going.A. had been; would have preventedB. had been; would preventC. were; would preventD. were; would have prevented( ) 6. He _____ you more help, even though he was very busy.A. might have givenB. might haveC. may have givenD. may give( ) 7. If it _____ for the snow, we _____ the mountain yesterday.A. were not; could have climbedB. were not; could climbC. had not been; could have climbedD. had not been; could climb( ) 8. Without electricity human life _____ quite difficult today.A. isB. will beC. would have beenD. would be( ) 9. A computer _____ think for itself, it must be told what to do.A. can’tB. couldn’tC. may notD. might not( ) 10. Jenny _____ have kept her word. I wonder why she changed her mind.A. mustB. shouldC. needD. would( )11. We _____ last night, but we went to the concert instead.A. must have studiedB. might studyC. should have studiedD. would study( ) 12. — Could I borrow your dictionary?— Yes, of course you _____.A. mightB. willC. canD. should( ) 13. Tom ought not to _____ me your secret, but he meant no harm.A. have toldB. tellC. be tellingD. having told ( ) 14. — If he _____, he _____ that food.— Luckily he was sent to the hospital immediately.A. was warned; would not takeB. had been warned; would not have takenC. would be warned; had not takenD. would have been warned; had not taken ( ) 15. Peter _____ come with us tonig ht, but he isn’t very sure yet.A. mustB. mayC. canD. will( ) 16. I told Sally how to get here, but perhaps I _____ for her.A. had to write it outB. must have written it outC. should have written it outD. ought to write it out( ) 17. I didn’t see your sister at the meeting. If she _____, she would have met my brother.A. has comeB. did comeC. cameD. had come ( ) 18. — Shall I tell John about it?—No, you _____. I’ve told him already.A. needn’tB. wouldn’tC. mustn’tD. shouldn’t ( ) 19. When a pencil is partly in a glass of water, it looks as if it _____.A. breaksB. has brokenC. were brokenD. had been broken( ) 20. It’s nearly seven o’clock. Jack _____ be here at any moment.A. mustB. needC. shouldD. can( ) 21.— There were already five people in the car but they managed to take me as well.— It _____ a comfortable journey.A. can’t beB. shouldn’t beC. mustn’t have beenD. couldn’t have been ( ) 22. Johnny, you _____ play with the knife, you _____ hurt yourself.A. won’t; can’tB. mustn’t; mayC. shouldn’t; mustD. can’t; shouldn’t ( ) 23. The fire spread through the hotel very quickly but everyone _____ get out.A. had toB. wouldC. couldD. was able to ( ) 24. — When can I come for the photos? I need them tomorrow afternoon.— They _____ be ready by 12:00.A. canB. shouldC. mightD. need( ) 25. — I stayed at a hotel while in New York.— Oh, did you? You _____ with Barbara.A. could have stayedB. could stayC. would stayD. must have stayed ( ) 26. — Will you stay for lunch?— Sorry, _____. My brother is coming to see me.A. I mustn’tB. I can’tC. I needn’tD. I won’t( ) 27. — Are you coming to Jeff’s party?—I’m not sure. I _____ go to the concert instead.A. mustB. wouldC. shouldD. might( ) 28. — Write to me when you get home.— _____.A. I mustB. I shouldC. I willD. I can( ) 29. I was really anxious about you, you _____ home without a word.A. mustn’t leaveB. shouldn’t have leftC. couldn’t have leftD. needn’t leave( ) 30. — Is John coming by train?— He should, but he _____ not. He likes driving his car.A. mustB. canC. needD. may专项练习（二）1. I didn’t see her in the meeting room this morning. She _____ at the meeting.A. mustn’t have spokenB. shouldn’t have spokenC. needn’t have spokenD. couldn’t have spoken2. One ought _____ for what one hasn’t done.A. not to be punishedB. to not be punishedC. to not punishedD. not be punished3. If you really want yourself to be in good health, you must ___ always ___ so much.A. not; be smokingB. not; have smokedC. not; to smokeD. be not; smoking4. With so much work on hand, you _____ to see the game last night.A. mustn’t goB. shouldn’t goC. couldn’t have goneD. shouldn’t have gone5. Most of the students felt rather disappointed at the English party. They say that it ______ better organized.A. had beenB. had to beC. must have beenD. could have been6. I’m surprised that he _____ in the exam.A. should failB. would have failedC. may have failedD. should have failed7. The little girl _____ there alone.A. not dare goB. dares not goC. dare not goD. dare not to go8. “Must we do it now?” “No, you _____.”A. won’tB. needn’tC. can’tD. don’t9. He said he would rather not _____ it right now.A. doingB. to doC. doD. to be doing10. You _____ to the meeting this afternoon if you have something important to do.A. needn’t to comeB. don’t need comeC. don’t need comingD. needn’t come11. Put on more clothes. You _____ be feeling cold with only a shirt on.A. canB. couldC. wouldD. must12. I _____ play football than baseball.A. would ratherB. had betterC. like betterD. prefer13. I thought you _____ like something to read, so I have brought you some books.A. mayB. mightC. couldD. must14. There was plenty of times. She _____.A. mustn’t have hurriedB. couldn’t have hurriedC. must not hurryD. needn’t have hurried15. The plant is dead. I _____ it more water.A. will giveB. would have givenC. must giveD. should have given16. You _____ return the book now. You can keep it till next week if you like.A. can’tB. mustn’tC. needn’tD. may not17. It’s still early, you _____.A. mustn’t hurryB. wouldn’t hurryC. may not hurryD. don’t have to hurry18. Please open the window, _____?A. can’t youB. aren’t youC. do youD. will you19. We _____ for her because she never came.A. mustn’t have waitedB. shouldn’t have waitedC. mustn’t waitD. needn’t wait20. — May I stop here? — No, you _____.A. mustn’tB. might notC. needn’tD. won’t21. It’s a fine day. Let’s go fishing, _____.A. won’t weB. will weC. don’t weD. shall we22. I didn’t see her in the meeting room this morning. She _____ at the meeting.A. mustn’t have spokenB. shouldn’t have spokenC. needn’t have spokenD. couldn’t have spoken23. — Please don’t make a noise. — _____. I’ll be as quiet as a mouse.A. Yes, I won’tB. No, I won’tC. No, I willD. Yes, I will24. The young man has made so much noise that he _____ not have been allowed to attend the concert.A. couldB. mustC. wouldD. should25. — Where is John? — He _____ in the library.A. should beB. must beC. can beD. must have been26. Since the road is wet this morning, _____ last night.A. it must rainB. it must be rainingC. it must have rainedD. it must have been rain27. — Will your brother stay home tonight?— I’m not quite sure. He _____ to the cinema tonight.A. must goB. can goC. may goD. may be going28. She’s already two hours late. What ______ to her?A. can have happenedB. may have happenedC. should have happenedD. must happen29. You must be a writer, _____?A. mustn’t youB. are youC. must youD. aren’t you30. I got up early that morning, but I _____ so because I had no work to do.A. mustn’t have doneB. didn’t need to doC. needn’t have doneD. can’t have done31. He _____ have come here yesterday, but he didn’t.A. couldB. shouldC. ought toD. all the above32. I missed the last bus, so I _____ go home on foot.A. mustB. have toC. mayD. had to33. He ought to win the first prize, _____ he?A. oughtn’tB. shouldn’tC. mustn’tD. both A and B34. Everyone _____ do his best for the modernizations of our country.A. canB. mayC. shouldD. might35. Let’s clean our classroom, _____?A. will youB. don’t weC. shall weD. do you36. Let us play basketball, ______?A. will youB. don’t weC. shall weD. do you37. He asked me for this book many times. Please tell him that he _____ have it tomorrow.A. mustB. mayC. shallD. both B and C38. “Your phone number again? I _____ quite catch it.” “It’s 9568442.”A. didn’tB. couldn’tC. don’tD. can’t39. Mother _____ us stories when we were children.A. was used to tellB. is used to tellingC. used to tellD. used to telling40. She would rather _____ more money on books _____ on clothes.A. cos t … notB. to spare … don’tC. pay … thanD. spend … than专项练习（三）1. — Has Li Lin started? He said he would join in the party.— He ______. He is a man of keeping his word.A. could have leftB. must have leftC. can’t comeD. won’t be c oming2. — May I park my car here?— No, you ______. No car is allowed to park here.A. may notB. needn’tC. mustn’tD. daren’t3. — Excuse me, could you tell me where the Yajia Supermarket is?—It’s two blocks straight ahead. You ______ miss it.A. mustn’tB. can’tC. needn’tD. shouldn’t4. — I saw Mr. Sun at Tongyu Station this morning.—You ______. He’s still on holiday in Hawaii.A. couldn’t haveB. mustn’t haveC. shouldn’tD. needn’t5. — How about paying a visit to Dr. Wang, our former Chinese teacher?— Good idea. I will e-mail him today so that he ______ know ______ to expect us.A. shall; whyB. could; whenC. would; whatD. will; how6. Everything has two sides. Beautiful songs, sometimes, ______ be just noise to others.A. mustB. mayC. shouldD. could7. Someone ______ my umbrella. I found it wet yesterday.A. must be usingB. must have usedC. must useD. must have been using8. — How dangerous it was!— Yes, but for the passer-by’s quick action, th e girl ______.A. was drownedB. could have been drownedC. had drownedD. should be drowned9. You ______ scold such a pupil who always keeps silent so seriously that you ______ hurt him.A. should; canB. may; willC. mustn’t; mayD. can’t; must10. — Why does Alice know so much about Angkor Wat?— She ______ have been there, or ...A. mustB. oughtn’t toC. mayD. can’t11. —You may laugh, but I’ve been thinking of becoming a vegetarian.— Oh, you ______ be crazy. You will be hungry all the time.A. mustB. mayC. willD. need12. —What’s the matter with you?—Oh, I’m not feeling well in the stomach. I ______ so much fried fish just now.A. shouldn’t eatB. mustn’t have eatenC. shouldn’t have eatenD. mus tn’t eat13. — ______ he have been chosen as captain of the football team?— Yes, he ______.A. Can; must haveB. Must; must haveC. Can; mustD. Must; must14. Mr. Zhang ______ in Shanghai tomorrow morning.A. can have arrivedB. will have arrivedC. may have arrivedD. must have arrived15. Miss Wang started at 8 o’clock, and she ______ be there now.A. shouldB. canC. can’tD. need16. — It must be Mr. Li who did it. — No, it ______ be Mr. Li.A. mustn’tB. wouldn’tC. can’tD. may17. You ______ finish reading the book as soon as possible.A. mayB. canC. needD. should18. — Need you go to work now? — Yes, I ______.A. mustB. needC. canD. dare19. Your trousers are dirty. ______ them for you?A. Shall I washB. Will I washC. Am I going to washD. Am I washing情态动词专项练习与解析一【练习解析】1．C 从原题中You can keep it till next week if you like这一信息句可知，“你不必现在还”。
高中英语语法之情态动词一、概念情态动词是表示能力,义务,必须,猜测等说话人的语气或情态的动词。
二、相关知识点精讲1．can1)表能力can 表能力时意味着凭体力或脑力或技术等可以无甚阻力地去做某事。
I can climb this pole.我能爬这根杆子。
He is only four , but he can read.他只有4岁，但已认得字了。
Fir e can’t destroy gold.火烧不毁金子。
因为 can 不能和其他助动词连用，所以表示将来式时用will be able to。
You will be able to skate after you have practiced it two or three times.你练习两三次后就会溜冰了。
2)表可能性多用于否定与疑问结构中，但也可用在肯定句中。
Can the news be true?这消息可能是真的吗？It can’t be true.它不可能是真的。
What can he possibly mean?他可能是什么意思？can 用在肯定句中表示理论上的可能性（一时的可能）。
Attending the ball can be very exciting.The road can be blocked.这条路可能会不通的。
may 在肯定句中表示现实的可能性。
The road may be blocked.这条路可能不通了。
3)表示允许（和 may 意思相近）常见于口语。
Can (May) I come in ?我能进来吗？Can I smoke here ?我可以在这里抽烟吗？2.could 的用法1)表过去的可能和许可，（多用于间接引语中）At that time we thought the story could not be true.那时我们认为所说的事不可能是真的。
Father said I could swim in the river.爸爸说我可以在河里游泳。
高中英语知识点归纳情态动词的用法和辨析情态动词是英语中的一类特殊动词，它们用来表示说话者对某种行为、能力、必要性等方面的态度或推测。
情态动词包括can, could, may, might, must, shall, should, will, would等。
它们在句子中有一定的用法和辨析。
一、can与could1. 表示能力与可能can用于一般现在时和一般未来时，表示肯定的能力或可能性；e.g. He can swim.（他会游泳。
）I can solve this problem.（我能解决这个问题。
）could则用于过去时，表示过去某一时间的能力或可能性。
e.g. When I was young, I could run very fast.（当我年轻的时候，我跑得很快。
）2. 请求与许可can用于一般现在时，表示请求或征询许可；e.g. Can I borrow your pen?（我可以借用你的笔吗？）Could则更加委婉，用于礼貌地请求或征询许可。
e.g. Could you please help me with the homework?（你能帮我做作业吗？）二、may与mightmay用于一般现在时和一般未来时，表示较正式的许可或征求对方意见。
e.g. May I use your phone?（我可以用你的电话吗？）might则表示过去或将来的一种可能性，常用于虚拟语气中。
e.g. If it rains tomorrow, we might stay at home.（如果明天下雨，我们可能会呆在家里。
）三、must1. 表示推测或推理must用于一般现在时和一般过去时，表示根据已有的客观事实或推理得出的合理推测。
e.g. He has been studying hard, so he must pass the exam.（他一直在努力学习，所以他一定会通过考试。
）2. 表示义务或必要性must用于一般现在时和一般过去时，表示说话者的主观认识或认为事物具有必然性或必要性。
