1. 含有条件状语从句的复合句(以do为例;S=主语)
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时 间 |
条件状语从句 |
主 句 |
|
与现在事实相反的假设 |
If +S+did… （一般过去时） |
S+would/should/could/might+do… If I were free today, I would go shopping with you. |
|
与过去事实相反的假设 |
If +S+had done… （过去完成时） |
S+would/should/could/might+have done… If I had been free yesterday, I would have gone shopping with you. |
|
与将来事实相反的假设 |
did… If+S should do were to do |
S+would/should/could/might+do… If I were to be free tomorrow, I might go shopping with you. |
注意事项：
1．倒装句。如果条件句中含有功能词had，should，were时，可以省去If，把功能词提前，构成倒装句。
2．错综条件句。若条件句和主句动作不存在同一个时间，则谓语形式应根据具体情况而定。
e.g.: If I hadn’t stood under the ladder to catch you when you fell, you wouldn’t be smiling now.又如：
(1)If I were you, I would have gone to the film last night.
(2)If we hadn’t got everything ready by now, we should be having a terrible time tomorrow.
(3)If the weather had been more favorable, the crops would be growing still better.
3．If there weren’t/had not been +…=without…
e.g.: If there hadn’t been your advice, I would have failed. = Without your advice I would have failed.
4．If it were not for…/ If it hadn’t been for…= but for…
5．otherwise+虚拟语气的句子
6．虚拟语气的句子，but+ 陈述事实的句子
2、 虚拟语气用在宾语从句中
2. wouldrather后的从句要用虚拟语气。
|
时 间 |
从 句 |
|
虚拟现在 |
were, did (动词一般过去式) |
|
虚拟过去 |
had done |
|
虚拟将来 |
did (动词一般过去式) |
例：Iwould rather I hadn’t said such unkind things to you. （虚拟过去）
I’d rather you came here for theanswer tomorrow morning. （虚拟将来）
I’d rather you posted the letter rightaway. (虚拟现在)
3. suggest+（that）S+should+do…
表示愿望、建议、请求等主观意向的动词之后的宾语从句，谓语用should＋动词原形，should常常省略。
这类词有：decide，demand，desire，insist，order，propose，suggest，recommend，request，require等。
注意：
1. suggest 当“建议”讲时，其宾语从句用虚拟语气；当“暗示、表明”时，用陈述语气
2. insist 当坚持“要求”时，宾语从句用虚拟语气；当坚持“某个事实”时，用陈述语气。
判断改错：（错）Your pale face suggests that you（should）beill.
（对） Your paleface suggests that you are ill.
（错）I insisted that you（should）bewrong.
（对）I insisted that you were wrong.
3. 虚拟语气用在主语从句中
It is demanded / necessary/ a pity + that…等结构的主语从句，谓语动词用should 加动词原形，should 可省略。
|
It is |
可用的词有三类 |
that |
（should）do |
|
suggested, ordered, required, proposed, demanded, requested, insisted等 |
|||
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important, necessary, natural, imperative, strange等 |
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a pity, a shame, no wonder等 |
4．虚拟语气用在同位语从句中。
某些表示建议、请求、命令等主观意向的名词后同位语从句需用虚拟语气，其表达形式为(should) ＋动词原形。
这类名词常见的有：advice，suggestion，proposal（提议），order，demand，desire，request，requirement，recommendation（推荐），plan，resolution（决议），idea等。
eg.We are all for your proposal that the discussion ( should )be putoff．
5．虚拟语气用在表语从句中。
某些表示建议、请求、命令等主观意向的名词作主语时，表语从句需用虚拟语气，其表达形式为(should) ＋动词原形。
这类名词常见的有：advice，suggestion，proposal，order，demand，desire，request，requirement，recommendation以及plan，idea，resolution等。
eg. My suggestion is that the mayor (should)present the prizes.
6．虚拟语气用在定语从句中
It is（about ／high）time＋that sb.did sth/should do sth..
eg. Don’t you think it’s about time we went home？
注：在thisis the first time ／second timethat．．．句型中，从句中谓语动词用陈述语气完成时态。
eg.Is this the first time that you have visitedHongkong？
7. 虚拟语气用在让步、方式、目的状语从句中
1．在带有even if/even though引导的让步状语从句的主从复合句中，主句和从句都用虚拟语气，动词形式与含有非真实条件句的虚拟语气相同。
如: Even if he had been ill, he would have goneto his office.
2．由as if或as though引导的状语从句表示比较或方式时。从句谓语形式为动词的过去式(be用were)或 “had十过去分词”。如: Hetreated me as if I were a stranger.
She talked about the film as if she had reallyseen it.
3．虚拟语气用在lest（唯恐、免得），forfear that及in case引导的目的状语从句中。 在由lest等引导的目的状语从句中需用虚拟语气，表示“以防，以免”等意思，其谓语动词多由should＋动词原形构成，should也可省略。
eg. He was punished lest he should make thesame mistake again．
8．虚拟语气用情感语言中
1．虚拟语气在表示客气、遗憾以及祝愿等场合中，使用虚拟语气。
eg.You shouldn’t have been following him soclosely；you should have kept your distance．
2．If onlysb./sth. +时态后退型的谓语 eg. If only I had known the result of theexamination.
