條件句
　　虛擬條件句主要有下面兩類(lèi):
　　表示現(xiàn)在及將來(lái)情況(表示純?nèi)患僭O(shè)或?qū)崿F(xiàn)的可能性不大的情況):
　　謂語(yǔ)主要形式如下(be多用were這個(gè)形式):
　　

從句	主句
過(guò)去式	would + 動(dòng)詞原形

　　If I were you, I wouldn’t lose heart.
　　How nice it would be if you could stay a bit longer.
　　表示過(guò)去情況的虛擬條件句(與事實(shí)完全相反的假設(shè)情況), 謂語(yǔ)主要形式如下:
　　

從句	主句
had + 過(guò)去分詞	would have + 過(guò)去分詞

　　She would have come if we had invited her.
　　If I hadn’t taken your advice, I would have made a bad mistake,
　　You wouldn’t have caught cold if you had put on more clothes.
　　有時(shí)候, 條件從句表示的動(dòng)作和主句表示的動(dòng)作, 發(fā)生的時(shí)間是不一致的(如一個(gè)是過(guò)去發(fā)生的, 一個(gè)是現(xiàn)在發(fā)生的). 這時(shí), 動(dòng)詞的形式要根據(jù)表示的時(shí)間來(lái)調(diào)整. 這種句子可以稱(chēng)為錯(cuò)綜時(shí)間條件句.
　　If he had received six more votes, he would be our chairman now.
　　If we hadn’t got everything ready by now, we should be having a terrible time tomorrow.
　　有時(shí)假設(shè)的情況并不以條件從句表示, 而是通過(guò)一個(gè)介詞短語(yǔ)來(lái)表示.
　　Without music, the world would be a dull place.
　　We could have done better under more favorable conditions.
　　That would have been considered miraculous in the past.
　　But for the storm, we should have arrived earlier.
　　如果條件句從句中包含有 were, had, should 或could, 有時(shí)可把if省略掉, 并把were, had, should或could放在主語(yǔ)前面.
　　Had we made adequate preparation, we might have succeeded.
　　Should there be a flood, what should we do?
　　Were it not for their assistance, we would be in serious difficulty.