My name is Tom Brown. I am an English boy. (1) I am twelve. I am a middle school student. From Monday to Friday I am very busy. We have six classes a day. At school, I like doing sports, (2) like playing basketball, tennis and soccer. So my favorite subject is P.E.. Mr. White is my P.E. teacher. He is very cool. After school, our P.E. teacher plays games with us. We students all like him. (3) I don't like math because it is too difficult for me. (4) But my math teacher Ms Smith says it is interesting and useful. So I must work hard on it.

等腰三角形的一边为4，另一边为9，则这个三角形的周长为（　　）

如图，在纸上剪下一个圆形和一个扇形的纸片，使之恰好能围成一个圆锥模型．若该圆的半径为1，扇形的圆心角等于60°，则这个扇形的半径R的值是____ .

①为避免伤害，我们应拒绝上网

②网络是把“双刃剑”，有利有弊，我们应趋利避害

③网络交往时要懂得保护自己

④网络交往使我们更加自由自在，我们应大力提倡网络交友