三、被動語態(tài)的用法

 (1)不知道或沒有必要說明動作的執(zhí)行者是誰。

例如：Some new computers were stolen last night.　一些新電腦在昨晚被盜了。(不知道電腦是誰偷的)

This bridge was founded in 1981.這座橋竣工于1981年。

 (2)強(qiáng)調(diào)動作的承受者，而不強(qiáng)調(diào)動作的執(zhí)行者。

  例如：The glass was broken by Mike.玻璃杯是邁克打破的。

  This book was written by him.這本書是他寫的。

　Your homework must be finished on time.你們的家庭作業(yè)必須及時完成。

四、主動語態(tài)變被動語態(tài)的方法

 (1)把主動語態(tài)的賓語變?yōu)楸粍诱Z態(tài)的主語。

 (2)把謂語變成被動結(jié)構(gòu)(be＋過去分詞) (根據(jù)被動語態(tài)句子里的主語的人稱和數(shù)，以及原來主動語態(tài)句子中動詞的時態(tài)來決定be的形式)。

 (3)把主動語態(tài)中的主語放在介詞by之后作賓語，將主格改為賓格。例如：

All the people laughed at him.

He was laughed at by all people.

They make the bikes in the factory.

The bikes are made by them in the factory.

He cut down a tree.

A tree was cut down by him.