必修三 U1 语法点 - 中

必修三Unit1 情态动词（一）情态动词梅may---might had better肯can---could be able to莎shall---should ought to used to将will---would would rather do骂死must have to你need爹dare一：情态动词的基本用法1.can、be able to 和could⑴can和be able to都表示能力，意思上没多大区别。

但can只有现在和过去时，而be able to则有更多的形式。

★但当成功地完成某一具体动作时，通常不用could而用was/were able to来表示。

这时was/were able to相当于managed to，表示经过一番努力，终于能够完成某事。

E.g. The wounded man still was able to get to the village and was saved in the end.⑵can和could①.表能力E.g. 1) Some of us can use the computer now, but we couldn’t last year.2) The new-built theatre can seat 1500 people.②. 表示推测，意为“可能”“或许”，用于疑问句或否定句E.g. 1) Can she be in the computer center?2) I thought what he said could not be true.③.表示“请求” “允许”(表请求时，口语中常用could 代替can 使语气更委婉，回答时用can)E.g.1) Can/Could I use your dictionary?2) Could you lend me a hand?④.表示“许可”，可与may 换用。

E.g. You can go home now.⑤. can用于疑问句或否定句中时，表惊异、不相信等，意思是“可能、能够”。

E.g. How can you say that you really understand the whole story if you have covered only part of the article?1. —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’t2. In the coal mine disaster, most of the workers were killed, but John ___have a narrow escape.A.couldB. wouldC. was able toD. can3. Mr. Bush is on time for everything. How ____ it be that he was late for the opening ceremony?A. canB. shouldC. mayD. must2.may/might(1). 表示“许可”或“请求”，有“可以”的意思，口语中常用might 代may , 表示委婉语气。

否定回答时用“must not”表“禁止，阻止”，不用“may not”. “may not” 表示“可能不” 。

E.g.1) --- -May I watch TV after supper?---- Yes, you may. / No, you mustn’t.2) Today is Sunday. She may not in her office now.⑵. 表示可能性。

意为“或许，可能” might 比may可能性小。

E.g. 1) It might be true.2) They may be in the library now.⑶. may/ might as well + 动词原形“…还是…的好” /“不妨”E.g. If that is the case, we may as well try.如果情况确实如此，我们不妨试一试。

⑷. May you +动词原形表“希望、祝愿、祈求” “祝你……”E.g. May you success.1.—Are you coming to Jeff’s party?—I’m not sure. I__________ go to the concert instead.A.mustB.wouldC.shouldD.might2.Sorry I'm late. I _____have turned off the alarm clock and gone back to sleep again.A. mightB. shouldC. canD. will3. will 与would(1). 表“请求、建议”等，用would 比用will 委婉，客气些E.g. 1)Will you lend me your book?2) Would you like a cup of tea?⑵. 用于表示意志或意愿。

will 指现在，而would 指过去。

E.g. 1) I’ll never do tha t again.2) They said that they would help us.⑶.表示习惯性动作。

译作“总是、惯于” will 指现在，would 指过去。

E.g. 1) He will often read all night.2) Fish will die without water.3) Every evening, she would sit by window, deep in thought.⑷. 表示功能，译作“能、行”⑸. 用于否定句中，表示“不肯、不乐意”E.g. No matter what I said, he won’t listen to me.4. should⑴. 用于表劝告、建议。

意为”应该、应当”。

E.g. You should keep your promise.⑵.用于表推测。

意为“可能、该…”E.g. 1) It’s 7 o’clock, he should be at home.2) They should have arrived by now.5. shall⑴shall作为情态动词用于第二,三人称，表示说话人的意愿，有“命令”、“警告、威胁、强制”和“允许”等意思。

E.g.1)You shall get the book tomorrow. 允诺2) He shall be punished. 警告3) You shall go with me. 命令4) If you will come to my house，I will show you my new painting.⑵在疑问句中，shall用于征求对方的意见或请求指示，常用于第一、第三人称。

E.g. Where shall he wait for us?/Shall we go out for a walk?⑶法律文件专用语----- of course.A. willB. shallC. wouldD. Do2.”The interest _______ be divided into five parts, according to the agreement made by both sides,” declared the judge.A. mayB. shouldC. mustD. shall6 must⑴. 表示义务或强烈的劝告，意为“必须”“应该”，其否定式表示“不应该”“不许可” “不准”“禁止”。

Eg: 1) You must finish your homework first.2) Children mustn’t speak like that to their parents.⑵. 回答must 所在的一般疑问句时，否定回答用“needn’t” “don’t have to”.Eg: ---Must we finish the work tomorrow?---No, you needn’t/ don’t have to, but you must finish it in three days.⑶. 表推测，用于肯定句，意为“一定”“务必”。

Eg: 1) Betty must be in the next room.2) He must be watering the flowers in his garden.★但当是否定的推测是用can’t ,而不是用mustn’t。

⑷mustn’t 表示禁止做某事。

例如：You mustn’t smoke in the office.--- He ______ some trouble for he looks dull.A. could have had B should have had C can have had D must have had2. -----Do you know where David is? I couldn’t find him anywhere.------Well. He ________have gone far-----his coat’s still here.A. shouldn’tB. mustn’tC. can’tD. wouldn’t7.比较have to和must⑴两词都是'必须'的意思，have to表示客观的需要，must表示说话人主观上的看法，既主观上的必要.E.g. My brother was very ill, so I had to call the doctor in the middle of the night.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）E.g. 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）⑵have to有人称、数、时态的变化，而must只有一种形式。

但must 可用于间接引语中表示过去的必要或义务。

E.g. He had to look after his sister yesterday. 他昨晚只得照顾他姐姐。

⑶否定结构中：don't have to表示"不必"，mustn't表示"禁止"。