英语将来过去式的用法为什么there is going to be a building there soon一定要用b

你这是两个问题,逐一回答如下：
1）第一个问题
　　不能说将来过去时,应该是过去将来时,其结构是 “would + 动词原形”,指的是发生在过去某个时候以后的行为.如：
He said to me that his mother would come and see him soon. [过去将来时would come and see 发生在said 以后]If I were you, I would not make friends with him. 要是我是你,我就不会和去他交朋友.[虚拟语气的过去将来时would not make在虚拟动词 were 以后]
2）第二个问题
　　There is going to be a building there soon 用的是存在句 there be,其结构是：
引导词：there谓语动词：is going to be主语：a building状语：there soon
　　句子的含义是 “那里不久会有（存在）一座楼”.如果改为 build a building,主语必须改用 “人”, 如 We are going to build a building. 意思是 “我们打算盖一座楼”.这两句话的区别是显而易见的.