围成一个图形的所有边长的总和叫做这个图形的____。

一个正方形的边长是12厘米，它的周长是____厘米。

看一看，下图是有什么图形组合而成的？

    It's sunny today. The sun is shining(照耀)in the sky and it's very hot. Nancy goes to the train station(车站)to meet her mother at noon. She walks in the street. There are no trees and she's fat. So she feels very hot. But she doesn't find (发现)a boy walking behind her. And she meets a friend and says "Hello" to him. "Who's the boy behind you?" asks(问) the man. Now she sees the boy. She is angry and asks, "Why(为什么) do you walk behind me, boy?" there's no shade(阴凉处) in the street, you know" answers the boy. "It's cool behind you, I think(想)."