情景

條件從句的謂語動詞

主句的謂語動詞

與現在事實相反

動詞過去式（be要用were）

should

+動詞原形

would

與過去事實相反

had +過去分詞

should

+have+過去分詞

would

與將來事實相反

１、動詞過去時

２、should +動詞原形

３、were to +動詞原形

should

＋動詞原形

would

注：如果條件從句謂語動詞包含有were或had, should, could有時可將if省去, 但要倒裝。如：Had you (If you had) invited us, we would have come to your party.

２、虛擬語氣在各種從句的應用

主語從句的虛擬

1. It is + adj. + that sb. (should) do

常見的形容詞有：necessary, important, strange, natural

It's important that he take my advice.

2. It is + n. + that sb. (should) do

常見的名詞有：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

常見的過去分詞有：suggested, advised, demanded, requested, required, asked, ordered,

proposed, decided, desired, insisted等。

It's requested that she go home as soon as possible.

賓語從句的虛擬

1. 表命令，表建議，表要求的動詞，后接賓語從句虛擬。虛擬的構成為(should) do。

I advise that he stay at home.

2. wish后接從句，虛擬的構成是往過去推一個時態。

I wish I had watched the football match last night.

注意以下幾組詞或短語用于虛擬語氣中。

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.

表語從句中的虛擬

在表語從句中，表示間接的命令，要求、請求、建議、決定等，主句中的主語通常是suggestion, proposal, request, orders, idea等。從句謂語形式是"(should)＋動詞原形"。如：

His suggestion is that we (should) leave at once.