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

從句	主句
過去式	would + 動詞原形

　　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), 謂語主要形式如下:
　　

從句	主句
had + 過去分詞	would have + 過去分詞

　　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, 條件從句表示的動作和主句表示的動作, 發(fā)生的時(shí)間是不一致的(如一個是過去發(fā)生的, 一個是現(xiàn)在發(fā)生的). 這時(shí), 動詞的形式要根據(jù)表示的時(shí)間來調(diào)整. 這種句子可以稱為錯綜時(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, 而是通過一個介詞短語來表示.
　　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.