What am I?

I am something that has four legs and only one foot,What am I?

The answer of yesterday's riddle is ：
Don't give him anything to eat for a while.

fast在谜题里不是＂快＂的意思，而是＂禁食＂的意思．这样谜题就是：你怎样让一匹慢马禁食？答案当然就是：有段时间不让他吃任何东西啦。