什么叫被动语态
被动语态(passive voice)是动词的一种形式，用以说明主语与谓语动词之间的关系。
英语的语态共有两种：主动语态和被动语态。
主动语态表示主语是动作的执行者，被动语态表示主语是动作的承受者。
被动语态是动词的一种特殊形式，一般来说，只有需要动作对象的及物动词才有被动语态。汉语往往用"被""受""给"等被动词来表示被动意义 。被动语态由“助动词be+及物动词的过去分词”构成。被动语态的时态变化只改变be的形式，
过去分词部分不变。疑问式和否定式的变化也如此。
被动语态通常为十种时态的被动形式,被动语态由“be+过去分词”构成，be随时态的变化而变化。以do为例，各种时态的被动语态形式为：
1 am/is/are +done (过去分词)一般现在时
Visitors are requested not to touch the exhibits.
2 has /have been done现在完成时
All the preparations for the task have been completed, and we're ready to start.
3 am/is /are being done现在进行时
A new cinema is being built here．
4 was/were done一般过去时
I was given ten minutes to decide whether I should reject the offer.
5 had been done过去完成时
By the end of last year, another new gymnasium had been completed in Beijing.
6 was/were being done过去进行时
A meeting was being held when I was there.
7 shall/will be done一般将来时
Hundreds of jobs will be lost if the factory closes.
8 should/would be done过去将来时
The news would be sent to the soldier's mother as soon as it arrived.
9 shall/will have been done将来完成时（少用）
The project will have been completed before July.
10 should/would have been done过去将来完成时（少用）
He told me that his new clothes would have been made very soon.
