七、情态动词
别妄想泡我
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2020年08月01日 05:02
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硫酸小檗碱-飙升的意思
【要点点拨】
1. 表示请求和允许: can, could , may, might. 过去式使语气更委婉，答语应用原形。
--- Could I use your computer tomorrow morning?
--- Yes, you can.( 否定回答可用：No, I’m afraid not.)
2．表示推测：
理论可能性 can
可能性 肯定句 must, may ,might, could
疑问句 can
否定句 can’t (不可能)，may not (可能不)
1)can表示理论上的可能性，指某事或情况可能发生，但并不说明实际上真的发生.
Children can be very tiring.
2)反意问句。 He may know the plan, doesn’t he?
You must have studied English before, haven’t you?
You can’ t have been caught in the rain last night, were you?
3．could & be able to
在肯定句中could表示过去有“能力”做，was / were able to表示过去有能力而且确实做成了某一件事， 相当于managed to do…或succeeded in doing sth.
The fire spread through the hotel very quickly but everyone was able to get out.
4. may / might as well do sth “还是…好”、“不妨”
You might as well tell me the truth. 你还是把真相告诉我的好。
5. must和have to
1) must表示的是说话人的主观看法, 而have to强调客观需要。
2）否定形式含义不同。mustn’t禁止，不许可，don’t have to不必
3) must 偏要（做令人不快的事）eg. Must you shout so loudly?
6. shall和should
1) 表示说话人征求对方意见和向对方请示，用于第一、三人称。
When shall my father be able to leave hospital?
shall 2)表示说话人给对方的命令、警告、允诺或威胁以及说话人的决心。
You shall go with me (命令) / You shall have the book when I finish it.（允诺）
He shall be punished （威胁）/ Nothing shall stop me from doing it. (决心)
1) 表示劝告和建议“应该”
2) “按道理应当”“估计”(=ought to)
They should be there by now, I think.
3） 用于第一人称表示说话人的一种谦逊、客气、委婉的语气。
I should advise you not do that.我倒是劝你别这样做。
should 4） 在条件句中表示“万一”，主句不一定用虚拟语气。
Ask Tom to ring me up if you should see him. /Should I be free tomorrow, I’ll come.
5） Why / How + should 结构表示说话人对某事不能理解，感到意外、惊异等意思， 意为“竟然”，也用在某些从句中。
It seems so unfair that this should happen to me.这种事竟然发生在我身上真不公平。
7. will 和would
1) 表示意志和意愿。will 指现在，would指过去。
If you will listen to me, I’ll give you some advice.
2) 表示请求、建议，would比will委婉、客气。Will (Would ) you please pass me the book?
3) 表示习惯性动作，“总是”“惯于”，will指现在，would指过去。
Fish will die without water.
Every evening, she would sit by the wind
ow, deep in thought.
4). 表示功能， 意为“能” 或“行” The machine won’t work.
5) 表示预料或猜想。It would be about ten when he left home.猜想他离开家时大约十点。
8. would & used to
1) 表示过去持续的状态和情况用used to; would不与表示状态的动词连用。
There used to be a hospital here. / There would be a hospital here.( ×)
2) would 常与often, sometimes, for hours等表示时间的副词（短语）连用。
We would sit in the yard every evening and listened to his story.
3) used to 强调过去的行为同现在的对比，含有“过去怎样，而现在却不这样了”的含义. eg. He will not spend the money on books as he used to.
9. dare 和need
两者作为情态动词都不用于肯定句，常用于否定句、疑问句和条件从句中。习惯用语I dare say（可能，或许，我揣测）除外。实义动词用法同于一般动词。但在否定句中，dare 后的to可省略，即：don’t / doesn’t dare (to ) do…. need 作为实义动词时，用在否定句中时，其后的to不能省略。
He dare go there alone. ( ×) He dares to go there.
He dares not go there alone. ( ×) He dare not go there alone . / He doesn’t dare ( to ) go there alone.
He stood there without daring lift his head.(×) He stood there without daring to lift his head.
10．情态动词+ have done,表示过去 比较： 情态动词+ do , 表示现在或将来。
cf. needn’t have done & didn’t need to do…
She need not have come yesterday. 她昨天本不必要来的。（但却来了）
She didn’t need to come yesterday. 她昨天不必来。（实际上也没来）
【各个击破】
1. I lived with my sister this summer and didn’t have to pay rent. So I ____ save most of my salary.
A. could B. would C. was able to D. should
2. --- Look , John’s fallen asleep.
--- Oh, he ______ too late last night.
A. might sit up b. should have sat up c. could sit up D. must have sat up
3. On Sundays when I was a child , Father and I ____ get up early and go fishing.
A. could B. would C. might D. should
4. --- Many people in England love to give advice on weather reporting.
--- Yes, but I think the weather office’s computers ___ be more accurate. (精确的)
A. can B. must C. ought to D. might
5. --- Are you still going to Shanghai for the Spring Festival?
--- Yes, but I really ____ because I have a lot of things to deal with.
A. can’t B. mustn’t C. won’t D. shouldn’t
6. –Well, I forgot to bring my dictionary here yesterday.
-- Actually you ____ it here. You were not allowed to use it.
A. needn’t bring B. needn’t have brought
C. didn’t need to bring D. don’t have to bring
7. --- Shall I book the table for the dinner?
---Yes, you____. The restaurant is always full of people.
A. can B. will