The result was not as good as expected but the ________ on his face told us that he was still very happy.

A．expression

B．impression

C．celebration

D．appearance

完成下列反应的化学方程式

（1）氢气在氧气中燃烧：______，

（2）大理石投入稀盐酸中：______，

（3）实验室用双氧水制取氧气（二氧化锰粉末作催化剂）：______，

（4）碱式碳酸铜加热分解______

（5）甲烷燃烧______