I am a dragon,but I can't fly.I am a snake,but I can't bite.I am a worm,

问题描述:

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.

这是个灯谜:答案是:桥
我是一条龙,可我不能飞.我是一条蛇,可我不能咬.我是一条虫,可是我可以不停地横穿小河.