There is going to be a dolphin show in the zoo tomorrow evening.为什么要加be?

There is going to be a dolphin show in the zoo tomorrow evening.为什么要加be？
There be 存在有句型 中的be 可以被下面内容替换，主语为 BE 后面的内容
(1) is / are /was/ were
(2) be going to
(3) will be
(4) happen /exist / stand/ live
(5) has /have been
(6) There appear to be
(7) There seemed to be

这是there be 句式的将来时态用法，它 的结构式 there is going to be 或者there are going to be .这个句式还可以用there will be 来代替，所以上面这句话还可以变成 There will be a dolphin show in the zoo tomorrow evening .

There is going to be = There will be 
哪里将会有什么事情发生


There is going to be a dolphin show in the zoo tomorrow evening
明晚动物园将会有一个的海豚表演节目

be going to 是将要的意思，这句中就等同于will，
there will a dolphin show 你就会发现，句中缺少谓语动词，所以必须加上be作为谓语。