See the flags on top of the building? That was we did this morning.
A. when
B. which
C. where
D. what
网友回答
A. when
B. which
C. where
(答案→)D. what
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。