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．

答案D
句意：“看到楼顶上的那些旗帜了吗？那是我们今天上午干的活。”that指“把旗竖起来”那件事。此处是what引导的表语从句，what在从句中作did的宾语。what还可引导主语从句和宾语从句。如：What I said is true．(what引导主语从句)。I don’t believe what he said．(what引导宾语从句)。that也可引导名词性从句，它与what的区别在于that在从句中不充当任何成分，只起连接作用，引导宾语从句还可省略，而what则充当成分，且不能省略。