—Do you often see William _____ on the playground?

—No, but he is often seen to play Chinese kung fu in the park.[ ]

A. run          

B. to run   

C. ran           

D. to running

在煤矿井下，一般（）等最易积聚瓦斯。

A．采煤工作面上隅角

B．微风或停风的掘进工作面

C．冒落的高顶处

D．停风的盲巷及煤仓