大學英語六級條件句語法精要

　　條件句 
　　虛擬條件句主要有下面兩類:
　　表示現在及將來情況***表示純然假設或實現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***與事實完全相反的假設情況***, 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.
　　有時候, 條件從句表示的動作和主句表示的動作, 發生的時間是不一致的***如一個是過去發生的, 一個是現在發生的***. 這時, 動詞的形式要根據表示的時間來調整. 這種句子可以稱為錯綜時間條件句.
　　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.
　　有時假設的情況並不以條件從句表示, 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, 有時可把if省略掉, 並把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.

大學英語四六級詞彙部分題型名詞詞義辨解
大學英語六級條件句語法精要