there is going to (be) a meeting in our school hall tomorrow evening请说原因

问题描述:

there is going to (be) a meeting in our school hall tomorrow evening请说原因

本句表示“明天晚上我们学校礼堂将有一场会议.”
有会议可以说“There is a meeting.”
be going to 表示“将要……”,to 后加动词原形,所以把There is a meeting中的is 变成了动词原形be.