與現在事實相反的虛擬語氣

請看下面的題目：

If he was here，he __________ us how to do it.

A. told                        B. would tell                        C. had told                        D. have told

此題應選 B。該題考查與現在事實相反的虛擬語氣：此時條件從句的謂語動詞用過去式，主句的謂語則要用 would (should，could，might)+動詞原形：

If there were no subjective mood，English would be much easier. 要是沒有虛擬語氣，英語就會容易得多了。

If I knew his telephone number，I would ring him up. 我要是知道他的電話號碼，我就給他打電話了。

在虛擬條件句，動詞be的過去式通常用were(不管是單數還是復數)，但在現代英語，單數情況也可以用was：(www.hz123456.com)

We could ask him if he were [was] here. 他要是在 這里，我們就可以問問他了。

但是在某些表達(If I were you，as it were等)中，be只用were這一形式：

If I were you，I should go and see the doctor at once. 假若我是你，我會馬上去看醫生。

The sky is covered，as it were，with a black curtain. 天空好像是被黑幕遮住了似的。

有時在虛擬條件句也可能用 could，might 等，那多半是因為語義的需要：

If he could help you，he would help you. 要是他能夠幫助你的話，他會幫助你的。