英语笑话:Where It Should Be Plugged（插在何处）

A mother is very good at using every chance to educate his son, who was only three years old. One day, she took a plug and said to her son, " Look, there are two pieces of copper, so it must be plugged in a place where there are two holes. Where do you think it should be plugged?" She waited for an answer expectfully ."Plug in nose." is the answer.