题目

As students, we should ____________ ourselves. We can't spend much time playing computer games. A . be responsible for B . be proud of C . be popular with D . be thankful to 答案：A铵明矾[NH4Al(SO4)2·12H2O]是分析化学常用基准试剂，其制备过程如下。下列分析不正确的是（ ）A.过程Ⅰ反应：2NH4HCO3＋Na2SO4=2NaHCO3↓＋(NH4)2SO4B.检验溶液B中阴离子的试剂仅需BaCl2溶液C.若省略过程Ⅱ，则铵明矾产率明显减小D.向铵明矾溶液中逐滴加入NaOH溶液并加热，先后观察到：刺激性气体逸出→白色沉淀生成→白色沉淀消失