注意：类似的表达还有sb do what one can to do sth；do/try one's best to do sth。 4．might/may as well最好……，还是……为好。 5．can not/never too＋形容词/副词
再……也不为过，越……越好。
虚拟语气
虚拟语气的概念
They insisted that the boy (should) go with them.
注意：suggest 当表示“暗示、表明“讲时，insist 表示”坚持认 为“之意时，应用陈述语气。 The smile on his face suggested that he was satisfied with our work.
Yes, you must. No, needn’t /don’t have to.
④ Need I finish it now?
Yes, you must. No, you needn’t.
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典型错误
1. He mustn’t be in the classroom. ( Can’t ) 2. You might leave the bag on the bag. ( might have left) 3. You must have seen the film last week, have’t you?
+ have +p.p 表示本应该做而未做。
Eg. You should have been five minutes ago.
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Will/ would
1、表示意愿
I’ll try my best to overcome the difficulty. 2、表示意图
What will you do? 3、表示请示
2
1. Can
1. 表示能力 The parrot can speak three languages. 2. 表示允许 Can I borrow the book from the library. 3. 表示可能性 Shanghai can be very cold in March.
Could 过去式；语气更委婉
Will you halp me to put these books in order? 4、表示习惯动作
She will sit for hours without saying a word.
Would 与 used to
1、Would 后只能接表示动作的动词。
2、used to 则还可以接表示状态的动词。 Eg. He used to be a worker.
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1、Shall /should
should 过去式 语气更委婉
1、第一、三人称疑问句中表示“请求 或征求对方意见。
Eg. Shall I get you a cup of coffee?
2、第二、三人称陈述句中
1、表示允诺 “会（得到）。
2、表示命令/警告 威胁 “该回必须”
2、shall/should ought to
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Dare / dared 1、情态动词用于否定、疑问句；条件从句中。
eg.
1. Dare you go here alone? 2. How dare you do such follish things? 3. I won’t allow you to swim in the river, even if you dare do it.
允许 3. 表示祝愿
Might 过去式；语气更委婉
Eg. 1. She may be still waiting for us.
2. May I come in?
3.May you have a happy holiday.
2. may/might + have +p.p
• 虚拟语气是一种特殊的动词形式，一是 用来表示说话人所说的话不是一个事实， 而是一种假设、猜测、怀疑等(在条件从 句中或让步状语从句中)；一是表示说话 人的愿望、要求、命令、建议等 (在宾语 从句、表语从句、同位语从句)。
与现在 事实相 反的假 设
一、虚拟语气在条件句中
虚拟条件句
主句
If+主语+动词的过去式 （动词be用were)
2、情态动词的过去式与原形相比，多点礼貌，少点冒昧， 语气更为委婉。
情态动词在一般疑问句中的回答： ① Can you sing? Yes, I can.
No, I can’t.
② May I come in? Yes, you may.
No, you mustn’t.
③ Must I handin the book now?
2. Must 、have to 与have got to
1. Must表示主观 2. Have to表示客观需求 3. Have got to 多见于口语
3. must + have +p.p 对过去事情的肯定猜测。
Eg. The road id wet. It must have rained last night.
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Ought to
1、其否定式为ought not to 2、ought to + have + p.p
表示本来应该做而没有做到。
Eg. You ought not to have cut away the trees around the old building.
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三点说明
1、情态动词 + v 表示对现在或将来动作的猜测。 情态动词 + have + p.p表示对过去动作的猜测。
二、虚拟语气在名词从句中的运用 （1）用于宾语从句
１、wish 后面的宾语从句中。 一般用虚拟语气，表示一种不可能实现的愿望。其谓语动词形
式为：
表现在 过去时 表过去 过去完成时 表将来 would, might, could＋动词原形
I wish (that) I were a bird. I wish (that) I had seen the film last night. I wish (that) I would\could go.
他脸上的表情表明他对我们的工作很满意． The man insisted that he had never stolen the money.
那个人坚持说他没有偷钱．
三、虚拟语气在其他从句中 1. It is (high / about ) time that…从句中的谓语动词用过 去式或should＋动词原形，should不能省略．
主语+should,would, might,could＋动词 原形
与过去 相反的 假设
If+主语+had +过去分词
主语＋should,
would, might, could ＋have done
与将来 相反的 假设
1、If+主语+动词过去式 2、If+主语+were to+ 动词原形 3、If+主语+should +动词原形
He treats /treated the boy as if he were his own son.
He speaks/ spoke as if he had known about it
2. Can 与 be able to
1. Can 表示习惯能力， 而be able to表示经过那里而做成了某事。
2. 在否定结构中，二者可以互换。
3. can./could + have +p.p
1.在否定、疑问句中表示“对过去发生行为 的可能性猜测。
2. 在肯定句中表示“本来可以做而未做”
1. The door was lacked. She couldn’t have been at home. 2. You could have been more careful.
3. would rather + 从句 动词用过去式或过去完成时
I would rather you told me the truth. I would rather you had gone there last Sunday.
4. as if ( as though) 看起来 常用虚拟形式，即表示与现在 事实相反，用过去式；与过去事实相反用过去完成式 (had done).
1.在否定、肯定句中表示对过去动作的推测 “也许是……”
2. Might+have+p.p表示虚拟，表“劝告、责备之意。
Eg. 1. He might have spoken to her yesterday. 2. You might have told me earlier.
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1. Must 1. 表示肯定的猜测,但只用于肯定句， 2. 而mustn’t 表示“禁止、不准”
主语＋should, would might, could＋动词
原形
２．省略句
在条件句中，可省略 if，把were ,had, should 提到句首，变为倒 装句式．
If I were at school again, I would study harder. Were I at school again, I would study harder. If you had come earlier, you would have met him. Had you come earlier, you would have met him. If it should rain tomorrow, we would not go climbing. Should it rain tomorrow, we would not go climbing.