Question

The fire destroyed _ was in building. A,all B .ALL that C.that D.which

Answer 1

选B，all that 相当于what，做的是destroy的宾语。
句子中缺少的即使destroy的宾语，有事从句的主语，双层身份的时候是what，但是没有what，再次可以用all that。
希望可以帮到你。