问题补充:
See the flags on top of the building? That was we did this morning.
A. when
B. which
C. where
D. what
答案:
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。