第五章 虛擬語氣 條件句（Conditional Sentences)

　　條件句有兩種，一種是真實條件句(Sentences of Real Condition)，表示一個可能實現的情況：

　　I'll help him if he asks me.

　　如果他向我提出，我可以幫助他。

　　If she isn't in, leave her a note.

　　如果她不在家，給她留一個條子。

　　另一種是虛擬條件句(Sentences of Unreal Condition)，表示一種純然假想的情況或實現的可能性不大的情況，這時動詞需用特殊形式，稱為虛擬語氣，虛擬條件句有兩種：

　　1.談過去的情況，動詞為：had+過去分詞, would have+過去分詞

　　If he had asked me, I would have helped him.

　　如果他向我提出了，我就幫助他。(但他沒向我提出)

　　If she had left five minutes earlier, she would have caught the train.

　　如果她早五分鐘動身，她就趕上火車了。(但動身晚了)

　　2.談現在或將求情況，動詞為：過去式would+動詞原型

　　If I had the money, I would travel round the world

　　如果我有錢我將作環(huán)球旅行。(但我沒有錢)

　　I would help you if I could.

　　如果能我是會幫助你的。(但不可能)

　　動詞為be時，多用were這個形式：

　　If I were you, I would accept the job.

　　我要是你我會接受這份工作。

　　有時if可以省略，這時后面要用倒裝語序：

　　Had I taken (=If I had taken) your advice, I wouldn't have made that mistake.

　　如果我聽了你的勸告，我就不會犯那個錯誤了。

　　Were I in your position, I would stay.

　　我要是處在你的地位我會留下。

　　條件從句 主句

　　had+過去分詞 would have +過去分詞

　　條件從句 主句

　　過去式 would +動詞原形