题目内容：

I am looking at the children _____volleyball.A.plays B.playing C.are playing D.to play

优质解答

I am looking at the children ___playing__volleyball.___playing__volleyball是对 the children的补充说明,也就是说孩子们正在打排球.I主语,am looking at 谓语,the children 宾语,playing volleyball宾语补足语....