高考英语语法完全讲解——情态动词（共24张PPT）

(共24张PPT)
高考英语语法完全讲解
情态动词
情态动词can和could常用来表示“能力”，强调能够做某事，can表示现在的能力，could表示过去的能力。另外，be able to表示经过一番努力能够做某事，而且成功做了某事。
I am very hungry. I can eat two bowls of rice.
When he was young, he could carry the heavy box.
The fire spread through the hotel quickly but everyone was able to get out.
情态动词表示推测时，对现在情况的推测用“情态动词+动词原形”，对过去情况的推测用“情态动词+have done”。情态动词表示推测时，可能大小排序如下：
must(一定)>will(很可能)>should/ought to(应该)>can(可能)>may(也许)>might(说不定)
He must know my address.
He can’t know my address.
He may know my address.
He may not know my address.
How can it be that he was late for the opening ceremony.（表示疑惑、惊讶）
He is not sure. He might go to the cinema instead.
The roads should be less crowded today.
特别提示：表示推测时，may常用于肯定句中，也可以用于否定句中（may not表示“可能不”），must用于肯定句中，一般不用于否定句和疑问句中，can和could常用于否定句和疑问句中，表示疑惑、惊讶或者不相信等意思。
1、may, might, can, could, will, would用于问句中，表示请求、许可或者提出建议；could/might/would表示请求时，语气更加委婉，肯定回答时，需要用can/may/will。
--Could/Might I use your bike tomorrow morning
--Yes, you can/may(No, you can’t/mustn’t).
2、shall在疑问句中与第一人称连用时，表示征求对方意见；在陈述句中与第二、三人称连用时，表示说话者的命令、指示、威胁、允诺、警告等。
You shall leave the room at once.
Anyone that disobeys the rule shall be fined.
Tom’s father promises that he shall buy his son a new bike on his birthday.
must表示主观上必须做某事，mustn't表示“禁止、一定不可以”，还可以表示“偏偏、偏要”，have to表示受客观条件的限制，不得不做某事。should表示应该做某事，有义务做某事，此外，should还可以表示“竟然、居然”。
Children mustn’t play with fire.
She must do anything against her parents’ will.
You should go and visit him this afternoon.
It is unbelievable that the poor man should help others.
Why should you be so late today
--Must I work out the problem tonight
--No, you needn’t/don’t have to.
1、need和dare
need和dare既可以用作情态动词也可以用作行为动词，用作情态动词时，常用于疑问句和否定句中；作行为动词时，有人称和数的变化，可用于肯定句、疑问句和否定句中，构成否定句和疑问句时，要借助助动词。另外，dare的过去式dared也可以用作情态动词。
He needn’t do it.
He doesn’t need to do it.
He didn’t dare to look at her in the face.
He dared not look at her in the face.
2、may as well和may well
may as well意为“最好、倒不如”，may well表示“很可能”。
You may as well do it at once.
Her appearance has changed so much that you may well not recognize her.
难点突破
must have done“过去一定做过某事”，对过去发生动作的肯定推测，否定式为：can’t/couldn’t have done“过去肯定没有做过某事”。
It must have rained last night, for the road is quite wet and muddy.
can/could have done“过去本能够做某事，实际上并没有做”。
You could have done better, but you didn’t try your best.
may/might have done“过去也许已经做过某事”，否定形式may/might not have done表示“过去可能没做过某事”；might have done还表示“过去本可能做某事，实际没有做”。
It’s too late. I think he may have gone to bed.
He may/might not have finished the work.
But I think you might have told us half an hour ago.
should/ought to have done表示“本应该做某事，实际上没有做”。
You ought to have done this exercise more carefully.
should not /ought not to have done表示“本不应该做某事，实际做了某事”。
You shouldn’t have told her the truth.
needn’t have done“本不需要做某事，实际上做了某事”。
You needn’t take a taxi here, for it was very near to my home.
would rather have done“宁愿做过某事，实际上当时并没有做”；否定形式would rather not have done“宁愿过去没做过某事，实际上已经做了某事”。
I raised objections at the meeting, but now I would rather not have done that.
would like/love to have done“本过去本想要做某事，实际上并没有做”。
I would love to have gone to the party last night, but I had to work extra hours to finish a report.