has it been announced when the plane is to take off中为什么用when

when they will come has no been announce中为什么要加been? It is _____(announce) that the Class One has won the game. it has been since.用法 It has been in my it is/has been= It's has been accepted it has long been assumed announce it's always been you(It has always been it has been可以缩写成it's been it's been.的全称是不是 it has been... It has been raining these days. It has been e()hot this week. it has long been known that it has since been rebuilt怎么翻译 造句it has been +时间段+since从句it has been +时间段+since从句 it has been used和it has been in use有什么区别吗 是It has been paid还是 It has been paid for?