四六级

2017英语四级基础语法复习:动词(15)

时间:2017-07-07 来源:文都网校 浏览: 分享:

      进入暑假状态的同学们都有什么安排与计划呢?有没有为学习英语留出一些时间?尤其是语法知识相对薄弱的同学,暑假正是恶补的最好时期。从今天开始小编每天为大家整理一些英语四级语法基础知识,希望大家认真复习。

            2017年12月英语四级基础语法知识大全

      must的用法

      1. 表示义务、命令或必要

      主要用于用于肯定句、否定句和疑问句。具体用法如下:

      (1)意为“必须”。如:

      Soldiers must obey orders. 军人必须服从命令。

      Something must be done to stop pollution. 必须采取措施来防止污染。(可跟被动语态)

      I think I must be going. 我想我得走了。(可跟进行时态)

      注:must 和have to 的用法及区别:

      must 和have to 都表示“必须”,有时二者可以通用,如:

      I must / have to leave now. 我得走了。

      must表示说话人的主观看法,have to 表示客观的需要。如:

      I feel I must write to thank you for your help. 我觉得我必须写信感谢你对我的帮助。

      It is raining hard. You have to take an umbrella. 雨下得很大,你得带把伞。

      must只有现在时形式;have to有更多时态。如:

      We had to be there at eight. 我们八点钟必须到那儿。

      “You'll have to get off here,” the conductor said. “你得在这里下车了,”售票员说。

      must用于宾语从句或间接引语中也可表示过去情况。如:

      He said that he must buy a gift for Mary. 他说他必须给玛丽买个礼物。

      She insists that I must do it by myself. 他坚持这事我必须独立完成。

      mustn't表示“禁止”“不许”;表示“不必”时,要用have to的各种形式。如:

      You must not go there. 你不准去那儿。

      We mustn't smoke here, must we? 我们在这儿绝不能吸烟,是吗?

      We don't have to buy a new radio. 我们不必买新收音机了。

      ⑤以must开头的疑问句,肯定回答用must, 否定回答用needn't 或don't have to.如:

      —Must I do it? 我一定要做这件事吗?

      —Yes, you must. (No, you needn't. / No, you don't have to.) 是的,一定要做。(不必。)

      (2)意为“应当”。如:

      We must have a discussion about it before making a decision. 再作决定之前我们应该讨论一下。

      You must read the book. 你应该读那本书。

      (3)表示必然性。如:

      Man must die. 人必有一死。

      What must be will be. 注定要发生的事总要发生。

      (4)表示与说话人愿望相反及不耐烦,意为“偏要”“偏偏”。如:

      Why must she keep on asking? 他干吗非要问个不停?

      We were ready to leave, the neighbor must come and chatter. 我们刚准备好要走, 邻居偏偏过来聊天。

      2. 表示推测

      must表示推测通常只用于肯定句,意为“准是”、“一定”,在否定句或疑问句用can。 如:

      (1) must+动词原形表示对现在情况的推测。如:

      You must be tired after your long journey. 你走了这么远的路,一定很累。

      It must be true. 那必定是真的。

      The man she married must have a lot of money. 她嫁的那个人一定有不少钱。

      (2) must+ have+ 动词的过去分词,表示对过去事情的推测。如:

      We must have taken the wrong road. 我们一定走错路了。

      He must have arrived there. 他必已到达那儿了。

      (3) must+ 进行式。

      表示对正在发生的事情的推测。如:

      Hurry up! Mother must be waiting anxiously. 快点!妈妈一定等急了。

      有时表示“即将┅”,“将要┅”如:

      I must be leaving now. 我得走了。.英语语法网 www.yingyuyufa.com

      有时must+ 进行式用来表示“老是在(干某事)”,如:

      Why must you always be finding fault with others? 你为什么老是挑别人的毛病?

      (4) must+ 完成进行式,表示“准是一直在┅”如:

      Someone must have been smoking here.一定有人一直在这里抽烟。

      They are sweating all over, They must have been playing football on the playground. 他们浑身是汗,准时在操场踢足球来着。

      can, could

      1) 表示能力(体力、知识、技能)。

      Can you lift this heavy box?(体力)

      Mary can speak three languages.(知识)

      Can you skate?(技能)

      此时可用be able to代替。Can只有一般现在时和一般过去式;而be able to则有更多的时态。

      I'll not be able to come this afternoon.

      当表示“经过努力才得以做成功某事”时应用be able to,不能用Can。如:

      He was able to go to the party yesterday evening in spite of the heavy rain.

      2) 表示请求和允许。

      -----Can I go now?

      ----- Yes, you can. / No, you can't.

      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 not. )

      3) 表示客观可能性(客观原因形成的能力)。

      They've changed the timetable, so we can go by bus instead.

      This hall can hold 500 people at least.

      4) 表示推测(惊讶、怀疑、不相信的态度),用于疑问句、否定句和感叹句中。

      Can this be true?

      This can't be done by him.

      How can this be true?

      may, might

      1) 表示请求和允许。might比 may语气更委婉,而不是过去式。否定回答时可用can't或mustn't,表示“不可以,禁止”。

      ----Might/ May I smoke in this room?

      ---- No, you mustn't.

      ---- May/Might I take this book out of the room?

      ---- Yes, you can. (No, you can't / mustn't. )

      用May I...?征徇对方许可时比较正式和客气,而用Can I...?在口语中更常见。

      2)用于祈使句,表示祝愿。

      May you succeed!

      3) 表示推测、可能性(不用于疑问句)。

      might不是过去式,它所表示的可能性比may小。

      1.He may /might be very busy now.

      2.Your mother may /might not know the truth.

      must, have to

      1) 表示必须、必要。

      You must come in time.

      在回答引出的问句时,如果是否定的,不能用mustn't(禁止,不准),而用needn't, don't have to(不必).

      ---- Must we hand in our exercise books today?

      ---- Yes, you must.

      ---- No, you don't have to / you needn't.

      2) must是说话人的主观看法, 而have to则强调客观需要。Must只有一般现在时, have to 有更多的时态形式。

      1. he play isn't interesting, I really must go now.

      2. I had to work when I was your age.

      3) 表示推测、可能性(只用于肯定的陈述句)

      1. You're Tom's good friend, so you must know what he likes best.

      2. Your mother must be waiting for you now.

      dare, need

      1) dare作情态动词用时, 常用于疑问句、否定句和条件从句中, 过去式形式为dared。

      1. How dare you say I'm unfair?

      2. He daren't speak English before such a crowd, dare he?

      3. If we dared not go there that day, we couldn't get the beautiful flowers.

      2) need 作情态动词用时, 常用于疑问句、否定句。在肯定句中一般用must, have to, ought to, should代替。

      1.You needn't come so early.

      2. ---- Need I finish the work today?

      ---- Yes, you must. / No, you needn't.

      3) dare和 need作实义动词用时, 有人称、时态和数的变化。在肯定句中,dare后面常接带to的不定式。在疑问句和否定句中,dare后面可接带to或不带to的不定式。而need后面只能接带to的不定式。

      1. I dare to swim across this river.

      2. He doesn't dare (to) answer.

      3. He needs to finish his homework today.

      shall, should

      1) shall 用于第一人称,征求对方的意见。

      What shall we do this evening?

      2) shall 用于第二、三人称,表示说话人给对方的命令、警告、允诺或威胁。

      1. You shall fail if you don't work hard.(警告)

      2. He shall have the book when I finish it.(允诺)

      3. He shall be punished.(威胁)

      will, would

      1) 表示请求、建议等,would更委婉。

      Will / Would you pass me the ball, please?

      2) 表示意志、愿望和决心。

      1. I will never do that again.

      2. They asked him if he would go abroad.

      3) would表示过去反复发生的动作或某种倾向。would表示过去习惯时比used to正式,且没有“现已无此习惯”的含义。

      1. During the vacation, he would visit me every other day.

      2. The wound would not heal.

      4) 表示估计和猜想。

      It would be about ten o'clock when she left home.

      should, ought to

      1) should, ought to表示“应该”,ought to表示义务或责任,比should语气重。

      1. I should help her because she is in trouble.

      2. You ought to take care of the baby.

      2) 表示劝告、建议和命令。should, ought to可通用,但在疑问句中常用should。

      1. You should / ought to go to class right away.

      2. Should I open the window?

      3) 表示推测

      should , ought to (客观推测), must(主观推测)。

      1.He must be home by now. (断定他已到家)

      2.He ought to/should be home by now.(不太肯定)

      3. This is where the oil must be.(直爽)

      4. This is where the oil ought to/should be.(含蓄)

      情态动词+不定式完成式(have done)

      1) can / could + have done在肯定句中表示“本来可以做而实际上能做某事”,是虚拟语气;在疑问句或否定句中表示对过去行为的怀疑或不肯定, 表示推测。

      1. You could have done better, but you didn't try your best. (虚拟语气)

      2. He can't have been to that town.(推测)

      3. Can he have got the book?(推测)

      2) may / might +不定式完成式(have done)

      表示对过去行为的推测。不能用于疑问句中,没有虚拟语气的用法。Might所表示的可能性比may小。

      1. He may not have finished the work .

      2. If we had taken the other road, we might have arrived earlier.

      3)must +不定式完成式(have done)

      用于肯定句中,表示对过去行为的推测。意为“一定、想必”。其疑问、否定形式用can,can't代替。参看1) can / could + have done表示推测。

      1. You must have seen the film Titanic.

      2. He must have been to Shanghai.

      4)should +不定式完成式(have done)

      用于肯定句中,表示对过去行为的推测。

      He should have finished the work by now。

      表示“本应该做而实际上没有做某事”,其否定式表示某种行为本不该发生却发生了。可以与ought to +不定式完成式(have done)互换。

      1. You ought to / should have helped him. (but you didn't.)

      2. She shouldn't have taken away my measuring tape, for I wanted to use it.

      5) needn't +不定式完成式(have done)

      表示“本来不必做而实际上做了某事”。

      You needn't have watered the flowers, for it is going to rain.

      6) will +不定式完成式(have done)

      主要用于第二、三人称,表示对已完成的动作或事态的推测。

      He will have arrived by now.

      希望以上内容可以帮助到对于英语语法有困惑的同学,想了解更多四六级备考课程备考资讯,请点击文都网校四六级资讯站查询!

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