求解一道高一英语题,在线等.

问题描述:

求解一道高一英语题,在线等.
Do you know where Mr.Write is?
Yes,He is fishing by the rever,with his son___beside him.
A playB.plays C.playing D.to play
请帮忙解答并说明理由,谢谢!

C,现在分词的独立主格结构作状语