The meeting has been called off. has后为什么加been. 谢谢

问题描述:

The meeting has been called off. has后为什么加been. 谢谢

正确答案为:
The meeting has been called off 会议已经被取消了.(会议是被取消的,要用被动)
现在完成时的被动语态 sth has/have been done