猜灯谜: I am a dragon,but I can't fly. I am a snake,but I can't bite. I am a worm,but I can cross,the river day and night.

问题描述:

猜灯谜: I am a dragon,but I can't fly. I am a snake,but I can't bite. I am a worm,but I can cross,
the river day and night.