被动语态的构成形式
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
The project will have been completed before July.
10） should/would have been done 过去将来完成时
He told me that his new clothes would have been made very soon
