题目

---Your head teacher has set up a Wechat group．Could you tell____？ ---It is more convenient to communicate with our parents． A．when it was set up     B．why did he set it up C．what it is used for    D．how did he set it up 答案：C下列几种物质均能使品红褪色，其中有一种物质使品红褪色的原理与其他几种不同，该物质是 （    ） A.过氧化钠　  　B.臭氧　　  C.二氧化硫　  　D.过氧化氢