│ │if从句(V) │主句(V) │
│现在│、动词的一般过去时或were│would (should, might, could)+动词原形 │
│过去│had十过去分词 │would (should，might，could)+have+ │
│ │ │过去分坷 │
│将来│should/were to+动词原形 │would(should, might, could)+动词原形 │
If my tooth went worse，I should have to have it pulled out.
I would not have made the mistakes if I had followed your advice.
If I were to tell him all I know，he would be amazed.
If he had followed my advice，he would recover already.
If it had not been for the teacher's help，it wouldn't be possible for us to succeed.
在if虚拟句中，有时将if省去，将谓语动词were或助动词did, had, should移至主语
Had she been given some information，she could have answered the questions.
Had we time to spare, we would be glad to go to the park.
Were it not for the discovery of electricity，the modern world would be cast in great in-
Should it rain tomorrow, we would stay at home.
Were it to rain，we would stay at home.
would as soon
had just as soon
I would rather you came tomorrow.
I'd just as soon you didn't behave like that.
I wish I were a freshman again.
I wish I could have gone to the movies with you last night.
3) It is time+从句(V用过去时表示虚拟，亦可用should+动词原形表示虚拟，这里
It is high time that you got (should get)dressed.
It is about time that this controversy were (should be) put an end to.
这里V二demand, insist, order, propose, move(提出动议)desire, require, request
advise,prefer, recommend, urge, decree(命令)，vote等。例如:
I moved that he be discharged for his serious mistakes.
The court decreed that he should pay the fine in full.
4. It Is ordered (suggested，demanded, moved，planned...)+that... 在这一句型中，that从句中的谓语动词须用虚拟式，即should+动词原形或将should
It was moved that more teachers (should) be sent to help them.
It was ordered that the books (should) be sent at once.
在和idea, necessity, plan, motion, order, proposal, recommendation, suggestion， un-
derstanding，agreement，desire，requirement，request，resolution, decision, advice等
Emphasis is laid on the necessity that all the objectives to be attained be taken into ac-
count before starting a new project.
My idea is that the group (should) hold another session to discuss the problem.
6. It is+adj.+that…(should)+V.. .
这里的形容词主要有以T一些:necessary, essential, fundamental, imperative, indis-
It is advisable that he (should) give up smoking.
It is appropriate that she (should) be dressed like that.
It is imperative that a meeting (should) be held at once.
注愈:上述形容词用在V + it + adj. +that…结构中同样须用虚拟式.例如:
The government deemed it indispensable that the prices (should) be controlled.
He considered it advisable that she (should)give up the plan.
有时虚拟的情况不用if引导的虚拟条件句来表述，而用介词如without, but for, but
that(接从句);或分词如supposing引出的从句;或并列连词如or, otherwise, but,
But for your help，the child would have been drowned.
He fled away，or he would have been arrested.
I would do so in your place.
Suppose there were no gravitational force，objects would not fall to the ground when