See the flags on top of the building? That was we did this morning

See the flags on top of the building? That was          we did this morning

A.when

B.which

C.where

D.what

答案及解析： D

解析：

主要测试表语从句。句子意思：看到那个建筑顶上的旗了吗？那就是我们今天早晨的杰作啊。分析句子结构可知：句子        we did this morning中动词did缺少宾语，另外该句子还要充当That was 的表语，因此双重作用的引导词只能选择what。