一，虚拟语气用于名词性从句
（1）虚拟语气在宾语从句中的运用。
①“wish + 宾语从句”表示不能实现的愿望，译为“要是……就好了”等。
表示现在不能实现的愿望，从句中的谓语动词用一般过去时；
表示将来不能实现的愿望，从句中的谓语动词用“would/could + 动词原形”；
表示过去不能实现的愿望，从句中的谓语动词用“had + 过去分词”或“could(should) + have + 过去分词”。如：
I wish it were spring all the year round.
I wish I had known the answer.
I wish I could fly like a bird.
②在表示建议、要求、命令的动词suggest、advise、propose、demand、require、insist request、command、order等后的宾语从句中，谓语动词用should + 动词原形或是动词原形。如：
She suggested we (should)leave here at once.
The doctor ordered she should be operated.
（2）虚拟语气在同位语从句和表语从句中的运用。
作表示建议、要求、命令等的名词advise、idea、order、demand、plan、proposal、suggestion、request等的表语从句和同位语从句，从句中的谓语动词用“（should） + 动词原形”。如：
His suggestion that we (should)go to Shanghai is wonderful.
My idea is that they (should)pay 100 dollars.
（3）虚拟语气在主语从句中的运用。
在主语从句中，谓语动词的虚拟语气用“should + 动词原形”的结构，表示惊奇、不相信、理应如此等。如：
It is necessary(important, natural, strange, etc.)that we should clean the room every day.
It was a pity (a shame, no wonder, etc.)that you should be so careless.
It will be desired(suggested, decided, ordered, requested, proposed, etc.)that she should finish her homework this afternoon.
注意：这种从句表示的是事实。如果说人对这种事实表现出惊奇的情感，就可用虚拟语气。反之，如果不表示惊奇等情感，that从句也可用陈述句语气。如：
It is pity that you can’t swim.
3、虚拟语气在其他场合的运用
（1）虚拟语气在as if/as though、even if/even though等引导的表语从句或状语从句中，如果从句表示的动作发生在过去，用过去完成时；指现在状况，则用一般过去时；指将来状况则用过去将来时。如：
He did it as if he were an expert.
Even if she were here, she could not solve the problem.
（2）虚拟语气用于定语从句中。
这种从句常用于句型“It is (high)time (that) … ”中，定语从句的谓语动词用一般过去时(be用were)或should + 动词原形，意思是“(现在)该……”。如：
It’s time that I picked up my daughter.
It’s high time we were going.
（3）虚拟语气用在if only引导的感叹句中。如：
If only I were a bird.
If only I had taken his advice.
（4）虚拟语气在一些简单句中的运用。
①情态动词的过去式用于现在时态时，表示说话人谦虚、客气、有礼貌或语气委婉，常出现在日常会话中。如：
It would be better for you not to stay up too late.
Would you be kind enough to close the door?
②用于一些习惯表达法中。如：
Would you like a cup of tea?
I would rather not tell you.
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