What go on four legs in the morning ,on two at noon and on three in the evening ? They are __?

问题描述:

What go on four legs in the morning ,on two at noon and on three in the evening ? They are __?
什么去四条腿在早上,中午两次,并在三个晚上?他们是__ ?

早上是小孩,中午是成年人,晚上是老人(加拐棍)