Unit 3  Understanding each other

(2)祈使語氣: 表示說話人的建議、請求、邀請、命令等。如: open the door, please。請打開門。
(3)虛擬語氣: 表示動作或狀態不是客觀存在的事實，而是說話人的主觀愿望、假設或推測等。如: if i were you, i should study english. 如果我是你，我就學英語了。may you succeed! 祝您成功！
二、虛擬語氣在條件從句中的用法
    條件句有兩類，一類是真實條件句，一類是虛擬條件句。如果假設的情況是有可能發生的，就是真實條件何。在這種真實條件句中的謂語用陳述語氣。如: if it doesn’t rain tomorrow, we will go to the park. 如果明天不下雨，我們就去公園。
如果假設的情況是過去或現在都不存在的，或將來不大可能發生的，則是虛擬條件句。如: if he had seen you yesterday, he would have asked you about it. 如果他昨天見到你，他會問你這件事的。(事實上他昨天沒見到你，因此也未能問你這件事。)
在含有虛擬條件句的復合句中，主句和從句的謂語都要用虛擬語氣。現將虛擬條件 從句和主句的動詞形式列表如下:
 從  句 主  句
與現在事實相反 動詞的過去式（be的過去式一般用were） would/ should/ could/ might + 動詞原形
與過去事實相反 had + 過去分詞     would/ should/ could/ might + have + 過去分詞
與將來事實相反     動詞過去式，should + 動詞原形，were to + 動詞原形 would/ should/ could/ might + 動詞原形
注: 主句中的should只用于i、we，但在美國英語中，should常被would代替；從句中的should 可用于各種人稱。
l. 表示與現在事實相反的假設和結果。如: if my brother were here, everything would be all right. 要是我哥哥在這兒, 一切都沒問題了。
   2. 表示與過去事實相反的假設和結果。如: if you had taken my advice，you wouldn't    (couldn’t) have failed in the exam. 如果你按照我的建議去做，你一定不會(不可能)考試不及格。
 3. 表示與將來事實可能相反的假設和結果。如: if it were sunday tomorrow, i should   (would，could，might) go to see my grandmother. 如果明天是星期天，我就 (可能)去看望我奶奶。if it were to snow this evening, they would not go out. 如果今晚下雪，他們將不出去了。
4. 在條件句中如果出現were, had, should可省去if，將主語與這些詞倒裝，例如：
              had the doctor come last night, the boy would have saved.
              were i to go to the moon one day, i would see it with my own e yes.
              should it rain tomorrow, we would stay at home.

for reference
relative items in recent years’ college entrance examination: