1. 当句子的主语是动作的执行者时，谓语的形式是主动语态。当句子的主语是动作的承受者时，谓语要用被动语态。被动语态由助动词be+过去分词构成，时态通过be表现出来。例如：
1）一般现在时：You are required to do this.
2）一般过去时：The story was told by her.
3）一般将来时：The problem will be discussed tomorrow.
4）现在进行时：The question is being discussed in the meeting room.
5）过去进行时：The new road was being made.
6）现在完成时：The novel has been read.
7）过去完成时：He said that the work had been finished.
8) 过去将来时：He said that the trees would be planted soon.
2. 一些特殊的被动结构
1）带情态动词的被动结构：
The problem must be solved soon.
2）带不定式的被动结构：
The homework needs to be done with care.
3）短语动词的被动结构：
例1）The baby is looked after carefully.
用于这类被动结构的短语动词要把它们作为整体看待。这类结构有以下几种：
①（不及物）动词+介词：agree to, ask for, call for, laugh at, listen to, look after, operate on, send for, talk about, think of等。
②（及物）动词+副词：bring about, carry out, find out, give up, hand in, make out, pass on, point out, put away, put off, take up, think over, turn down, turn out, wipe out, work out等。
③动词+副词+介词：do away with, face up to, give in to, look down upon, make up for, put up with等。
例 2) Attention must be paid to your pronunciation.
用于这类被动结构的短语动词最多见的是“动词+名词+介词”这一结构。如：catch sight of, keep an eye on, make use of, make a fool of, pay attention to, put an end to, set fire /light to, take care of, take hold of, take notice of等。
例 2与例1的不同点在于，它们用于被动时态能有两种形式。第一种形式是把“动词+名词+介词”作为整体看待。第二种形式是把其中的“动词+名词”作为“动词+宾语”的结构处理。
4）带复合宾语的动词在改为被动语态时，一般把主动结构中的宾语改成主语，宾语补足语保留在谓语后面。例如：
We always keep the classroom clean.
(比较：The classroom is always kept clean.)
5）有些动词形式上是主动结构，但表示被动的意思。常见的有可和well, easily等副词连用的不及物动词sell, wash, write, read, clean, cook等。例如：
The cloth washes well.这布很经洗。
The new product sells well.这新产品很畅销。
The pen writes well.这枝笔很好用。
6）下列情况主动句不能改成被动句：
①谓语是及物动词leave, enter, reach, suit, benefit, lack等。
②谓语是不可拆开的短语动词take place, lose heart, belong to, consist of等。
③宾语是反身代词，相互代词，同源宾语，不定式，动名词，抽象名词等。
7）汉语有一类句子不出现主语，在英语中一般可用被动结构表示。例如：
据说…… It is said that …
希望… … It is hoped that …
据推测说… … It is supposed that …
必须承认… … It must be admitted that …
必须指出… … It must be pointed out that …
众所周知… … It is well known that …
有人会说… … It will be said that …
大家认为… … It is generally considered that …
有人相信… … It is believed that …
注意：这种结构可改为“Sb/Sth + be + pp + 动词不定式” 。例如：
It is said that Tom has got the first place in the exam.=Tom is said to have got the first place in the place.
It was reported that her mother died of SARS.=Her mother was reported to have died of SARS.
3. 主动表示被动含义
主动表示被动含义的句子的主语通常是表示物的词（指人的极少），而且这种物都具有某种内在的特点，能够促进动词所表示的动作得以实现或难以实现。这时的动词一般是不及物动词。例如：
Your speech reads well.
The dinner is cooking.
The cloth has worn thin.
The door won’t lock.
The windows blew open.
The food tastes sweet.
比较：
The girl does not photograph well.(强调女孩的特点，不上照。)
The girl has not been photographed well.（与女孩本人无关，在于摄影师没有照好。）
选我吧，打了好久的。
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