What goes on four legs in the morning，on two at noon，and o(2)

答案是：People.They crawled when they were babies and walked with two legs before they had to rely on a crutch in old age.

是人，他们刚生下来的时候用四肢爬行，后来用双腿走路，老年时又不得不依靠拐杖走。