被动语态
英语动词有主动和被动两种语态。主动语态（active voice）表示主语是动作的执行者。被动语态（passive voice）表示主语是动作的承受者。 例如：He wrote a letter this morning. 句中主语He是谓语动词 wrote这个动作的执行者，因此谓语动词 wrote采用这种主动语态形式。如果变为：A letter was written by him this morning.句中主语 A letter 是谓语动词动作的承受着，因此这时谓语动词采用was written 这种被动语态形式。原主动语态结构中的主语He 在被动语态结构中则变为介词短语by him，在句中作状语。
一、 被动语态的形式
被动语态由助动词be加及物动词的过去分词构成。助动词be有时态、人称和数的变化。现以动词give为例，将各种时态被动语态的形式列表如下：
时一般 进行 完成 间 体 现is（am，are）is ( am, has (have) 在 given are ) been given being given 过was (were) was had been 去 given (were) done being given 将will ( shall ) be ----------------来 given -------------- - 过would(should)b ----------------去e given -------------- 将- 来 理论上讲，被动语态的时态可以有十二种，但实际常用的时态只有上表中的八种。
二、 被动语态的用法
被动语态常用于以下情况：
1．当我们不知道谁是动作的执行者时。例如：
Printing was introduced into Europe from China.
His car was stolen a week ago.
In that case no water would be brought to the river.
2．当我们认为没有必要指出或不想指出谁是动作的执行者时。 例如：
Television ads are usually repeated over and over again.
No decision has been made so far/
Many programe s are now televised in color.
She was given so much without having to do anything in return.
A child is constantly being told not to do
this or that or being punished for what he has done wrongly.
3．虽然需要同时指出动作的执行者，但我
们强调或突出的是动作的承受者，此时动作的执行者用介词by加代表动作执行者的名词或代词表示。例如： The book “Treasure Island”was written
in 1883 by Robert Stevenson, a British writer.
A special apparatus was used by the
psychologist to study shorterm memory. Her plan has been approved by the
management.
三、 被动语态的几种特殊结构 1． 含有情态动词的被动语态结构 2． 短语动词的被动语态结构
所谓短语动词，指的是某些动词和其他词类，如介词、副词、或名词+介词等构成的固定词组。例如：
依靠，取决于 （动词+介词） 关掉（动词+副词）
继续（动词—+副词+介词） 利用（动词+名词+介词）
短语动词应作为一个整体看待，变为被动语态是不能丢掉构成短语动词的介词、副词
+介词等成分。例如
We have sent for the doctor. The doctor has been sent for.
We shall put off the meeting till Fraday. The meeting will be put off till Friday.
People looked down upon women in the past.
Women were looked down upon in the past
The nurse takes care of the children The children are taken care of by the nurse. 3. 含有两个宾语的主动结构变为被动结构 We allowed him an hour to get to the airport.
He was allowed anhour to get to the airport.
An hour was allowed him to get to the airport.
4. 含有复合宾语的主动结构变为被动结构 We advised him to practice speaking English.
He was advised to practice speaking English.
5. 英语中有很多动词可用主动形式表示被动意义，汉语中这种结构更常见。
The cakes sell quickly. ( The cakes are sold quickly. )
The car drove easily. ( The car was driven easily. )
The fields flooded. ( The fields were flooded. )
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