英语语法问题,关于复合句的

问题描述:

英语语法问题,关于复合句的
In the A.D.300's,a church was built over _______ was thought to be Saint Perter's Tomb.
这里答案是what.有点不能理解.where的话我想很多同学都会填这个的吧.我首先来分析下,what was thought .做的是over 的宾语,而what既做over的宾语,也做它引导的宾语从句的主语.
但是我看了下语法书,where应该也有同样的功能吧,意思是没有看到可以排除where的语法,可能是我看漏了,但是找了几次的确没有找到.

In the A.D.300's, a church was built over _______ was thought to be Saint Perter's Tomb.
In the A.D.300's, a church was built over【what】 was thought to be Saint Perter's Tomb.
应该填what.因为what=the thing which/ that.我问题说了一大堆,其实我是想知道为什么where不可以,where = the place where??我问题说了一大堆,其实我是想知道为什么where不可以,where = the place where??where = the place where,但是where是副词,不能做介词over的宾语,也不能做was的主语,你说是吗?where是可以作为关系代词吧,而且在这里用where的话也是关系代词吧?where不能作关系代词,where只能做【关系副词】。