读“中国主要山脉分布图”，回答下列问题：
“这里的水却是镜一样子，蓝天容易清，拉长的水草在水底轻轻的浮动。”此处环境描写的作用是：____
A:I called you yesterday. You didn't answer it. B:Oh, sorry. I_ in the bathroom at that time.
