19.I’ve never seen anyone run so fast--_____ David go.

问题描述:

19.I’ve never seen anyone run so fast--_____ David go.
A.just watch B.just to watch
C.just watching D.just having watched
知识点是什么?

答案a“--”是破折号 后面的表示说明
而这里的内容显然是祈使句