虚拟语气在从句中的运用
A）用于宾语从句中。
wish +从句，表示不可能实现的愿望。
wish that…had done…（过去）
wish that…did/were… （现在）
wish that… would/could do…（将来）
如：
We wish we had arrived there two hours earlier.
I wish I were a bird.
I wish you could come tomorrow.
用于表示建议、愿望、命令等词后的宾语从句中，常见的动词有：suggest, insist, command, advise, desire, order, request, require, demand that…(should) do…
例句：
We insisted that she (should) go with us.
He suggested that we (should) start off early the next day.
The doctor ordered that the patient ( should ) be sent to hospital without delay.
They insisted that the boy (should ) go with them.
注意：当suggest表示“暗示、表明”之意时，不用虚拟语气，应用陈述语气。如：
The smile on his face suggested that he was satisfied with out work.
当insist表示“坚持认为”之意时，不用虚拟语气，应用陈述语气。如：
The man insisted that he had never stolen the money.
在would rather, had better 后的宾语从句中，也用虚拟语气，其构成为动词过去式。如：
I would rather they didn't hear of the news.
B) 用于主语从句中
It is desired /suggested /proposed/necessary/important/strange/natural/a pity + that 从句。从句中的谓语动词用“should + 动词原形”，should 可以省略。如：
It is suggested that the meeting should be put off till next week.
It is strange that he should have acted toward his parents like that.
注：以上句式也可以用陈述语气。如：
It's strange that he didn't come yesterday.
It's a pity that you can't dance.
C) 用于表语从句和同位语从句中。
在suggestion, proposal, order, plan, idea, request, advice等名词后的表语从句和同位语从句中要用虚拟语气。其构成是“should + 动词原形”。如：
My idea is that we should think it over before accepting it.
We all agreed to his suggestion that we should go to Dalian for sightseeing.
三、虚拟语气用在as if (as though), even if (even though)等引导的表语从句或状语从句中。
表现在：用过去时；表过去：用过去完成时态；表将来：用过去将来时态。如：
He looks as if he were an artist.
She speaks English so fluently as if she had studied English in Ameirca.
Even if he were here, he could not solve the problem.
四、虚拟语气用于定语从句中。
It is (high) time (that)……（此句型意为“现在该……”，用来表示提议）句型中，定语从句的谓语动词用过去式，或should + 动词原形（其中should 不能省略）。如：
It is (high) time that you went to school.
It is (high) time that we should start now.
五、用于if only 引导的感叹句中。
If only I were a flying bird!
If only I had seen the film!
六、在含有If it were not for或If it had not been for条件句的虚拟语气中。
If it were not for the rain, the crops would die.
If it had not been for your help, we couldn't have finished the work ahead of time.
七、用于表示委婉语气的句型中。
It would be better for you not to do that.
Would you be so kind as to show me the way to the railway station?
Could you please help me with this heavy bag?
八、用于“may + 动词原形”表示“祝愿……”，may 须置于句首。
May you succeed!
May you be happy!