情景
条件从句的谓语动词
主句的谓语动词
与现在事实相反
动词过去式（be要用were）
should
+动词原形
would
与过去事实相反
had +过去分词
should
+have+过去分词
would
与将来事实相反
１、动词过去时
２、should +动词原形
３、were to +动词原形
should
＋动词原形
would
注：如果条件从句谓语动词包含有were或had, should, could有时可将if省去, 但要倒装。如：Had you (If you had) invited us, we would have come to your party.
２、虚拟语气在各种从句的应用
主语从句的虚拟
1. It is + adj. + that sb. (should) do
常见的形容词有：necessary, important, strange, natural
It's important that he take my advice.
2. It is + n. + that sb. (should) do
常见的名词有：a pity, a shame, no wonder, one's wish
It's a pity that he be so silly.
3. It is + done + that sb. (should) do
常见的过去分词有：suggested, advised, demanded, requested, required, asked, ordered,
proposed, decided, desired, insisted等。
It's requested that she go home as soon as possible.
宾语从句的虚拟
1. 表命令，表建议，表要求的动词，后接宾语从句虚拟。虚拟的构成为(should) do。
I advise that he stay at home.
2. wish后接从句，虚拟的构成是往过去推一个时态。
I wish I had watched the football match last night.
注意以下几组词或短语用于虚拟语气中。
1. as if, as though
He speaks English as if he were a native speaker.
2. otherwise, but, even though
He was ill. Otherwise he would have been there.
3. with, without, but for
Without your help, I would have died two years ago.
But for your help, I would have died two years ago.
4. would rather I'd rather you told me yourself.
5. It's time that
It's time that you went to bed.
It's time that you should go to bed.
表语从句中的虚拟
在表语从句中，表示间接的命令，要求、请求、建议、决定等，主句中的主语通常是suggestion, proposal, request, orders, idea等。从句谓语形式是"(should)＋动词原形"。如：
His suggestion is that we (should) leave at once.
