题目内容：

the announcement---------greatly distressed the waiting passengers
that all flights were cancelled why all flights were cancelled 知道是用同位语从句或定语从句 但why all flights were cancelled这个不知道错在哪了,

优质解答

是同位语从句,用that all flights were cancelled,补充说明annoucement的内容.
如果用why引导从句的话,前面的名词需要表示“原因”,why不能跟annoucement搭配.类似的搭配都有规律可循的,比如说时间配when,地点配where等等.