When the plane is to take off has not been announced 飞机何时起飞还没有宣布飞_英语解答

When the plane is to take off has not been announced 飞机何时起飞还没有宣布
飞机何时起飞还没有:When the plane is to take off has not
为什么这边需要用过去分词加announced这是什么形式.?

人气：160 ℃　时间：2019-08-21 09:46:41

解答

announce 是人为动作所以主语为 When the plane is to take off 起飞时间的时候主语是被announce 所以是 be announced
时间是被人宣布的