23.The fire destroyed ____ was in the building.A.all B.what C.that D.which 这些句子的结构,为什么要选择这样的答案和这些句子的意思

你看，整个主句缺什么，主谓都有了，而destroyed是及物动词，所以缺宾语，所以用名从．
所以这里用WHAT

what可以理解为all that
The fire destroyed all that was in the building.
大火毁了楼里的一切

大火把大楼里的一切都烧毁了
这是一个定语从句,在这里 what=all that 现在明白了吧,其实就是下面这个句子
The fire destroyed all that was in the building
that was in the building为定语,修饰all