题目

 No one knows ____________ made her mother so upset with her. A. why it is that        B. what is it that   C. why is it that    D. what it is that 答案：D下列反应属于分解反应的是（　　）A．木炭在氧气中燃烧B．蜡烛在空气中燃烧C．铜绿受热D．镁带在空气中燃烧