I often see the girls in the room. They are very pleased.A. danceB. dancesC. dancingD. to

问题补充：

I often see the girls in the room. They are very pleased.

A. dance

B. dances

C. dancing

D. to dance

答案：

(答案→)A. dance

B. dances

C. dancing

D. to dance

解析：此题重点考查see sb do sth和see sb doing sth的区别。都表示看到某人做某事。前者表示看到某人经常做某事或做过某事；后者表示看到某人正在做某事。根据语境可知我经常看到女生们在房间里跳舞，她们非常开心，故选A。