题目

Every year thousands of young people in England finish school and then take a year off before they start work or go to university. Some young people go to other countries and work as volunteers. Volunteers give their time to help people. For example, they work in schools of hospitals, or they do something helpful for the environment.Pauline Jones, 18, lives in Cardiff, Wales. Next year she wants to go university to study Chinese, but now she’s living in Belize. Pauline says, “I’m working with other people here to save the coral reefs(珊瑚礁) in the sea near Belize. The reefs here are 如图是密闭体系中某气体反应的微观示意图，“”，“”分别表示不同的原子．（1）在反应后的方框内应填入下列微粒    （选填序号）A．   B．  C．（2）写出符合微观图示的一个具体反应的化学方程式    （3）与两种物质在构成上的不同点是    ．