英语有两种语态， 主动语态和被动语态， 主动语态表示主语是谓语动词动作的执行者，被动语态表示主语是谓语动词动作的承受者。例如：
I have repaired the radio.
The radio has been repaired.
The students cleaned the classroom.
The classroom was cleaned by the students.
be + 过去分词
A building was damaged by the storm.
Our plate was made in China.
My bike was stolen.
常用的被动语态的时态变化如下，以 ask 为例：
一般 进行 完成
现在I am asked, I am being asked, I have been asked
过去I was asked,I was being asked,I had been asked
将来I shall be asked, I shall have been asked
过去将来I shall be asked
Has your TV set been repaired?
Was the kite broken?
Has the work been done?
The letter has not been sent out.
The little boy has not been found out.
The cap has not been mended yet.
Their money has not been sent to them.