1;What is "four feet on four feet waiting for four feet?2;What is the center of gravity?3;What never asks questions but always gets answers?4;Why don't babies need glasses?5;What do you drop when you need it and take back when you don't?6;What's the difference between a monkey and a flea(跳蚤)?7;What 5-letter word has six left when you take 2 letters away?8;When Columbus discovered America,where did he stand?9;When the boy fell into the water,what's the first thing he did?10;What is black when it is clean and white when it is dirty?