图中A～E是操作化学常见的物质，已知A和E都可以作燃料，其中A是天然气的主要成分，请分析回答：

（1）反应①的化学方程式为　____ ；

（2）反应②中的产物B通常用____；

（3）E物质作燃料的优点是____（答一条即可）．

cos(arcsin$\frac{1}{2}$)的值为（　　）

阅读理解

   Tom is thirteen years old．He is in Grade Seven this year．He likes playing football and watching football matches．And he often reads newspapers．He does his best to know when and where there is going to be a football match．Now Tom is having

lunch and he is also reading newspapers．He is very happy because there is going to be a nice football match on TV at four this afternoon．He wants to watch it very much，but he is going to have English and maths lessons h the afternoon．He thinks hard and finds a way．

    “Hello，Mrs. Black，”Tom says to his teacher on the telephone．“Tom is ill in bed．H e wants to ask for half a day's leave(请半天假)．”

    “Oh，I'm sorry to hear that，”says Mrs. Black．“But who is that?”

    “It's my father，Mrs. Black，”Tom answers．