几种不同形式的被动语态

（1）含有直接宾语和间接宾语的主动结构，变为被动结构时，可以将其中一个宾语变为主语，另一个不动，一般是主动结构的间接宾语变为被动结构的主语，这样句子显得自然一些。如：

He showed me his pictures.

I was shown his pictures by him.

I was sent a birthday present (by him).

A birthday present was sent to me (by him).

（2）含有复合宾语的主动句变为被动句的方法。

① 将宾语变为主语，宾语补足语保留不动。如：

They call her little Li.   She is called little Li.

He left the door open.   The door was left open by him.

② make, let, hear, watch, see, feel, have, notice, help等动词后面作宾语补足语的不定式一般不带to，可是当变为被动语态时，后面的不定式必须带to。如：

My brother often made me do this and that when I was young.

I was often made to do this and that by my brother when I was young.

③ 含有情态动词的被动语态，是由“情态动词 + be +（及物动词的）过去分词”构成。如：

They can not find him.

He can not be found.

④ 短语动词的被动语态

一般说来，只有及物动词才有被动语态，因为只有及物动词才可能有动作的承受者。但有许多由不及物动词加介词及其他词类构成的短语动词，相当于及物动词，可以有宾语，因而也可以有被动语态。但应注意，短语动词是一个不可分割的整体，在变为被动语态时，不可丢掉构成短语动词的介词或副词。如：

They had put out the fire before the fire brigade arrived.

The fire had been put out before the fire brigade arrived.

They will set up a new public school here.

A new public school will be set up here.

You must take good care of these trees.

These trees must be taken good care of.

被动语态的基本用法

① 不知道谁是动作的执行者或者没有必要指出谁是动作的执行者时。如：

Paper is made from wood.

The house is quite old, it was built in 1950.

He was wounded in the fight.

② 需要强调动作的承受者时。如：

Calculator can’t be used in the maths exam.

Books and newspapers in the reading room mustn’t be taken away.

He was awarded first prize in that contest.

③ 为使语气婉转，避免提及自己或对方而使用被动语态，或由于修辞的需要使用被动语态使句子得以更好安排。如：

The construction of the new lab must be completed by the end of next month.

Electricity is used to run machines.