题目

Tom has been absent for two days．Do you know what _________ to him?       A．has happened   B．would happen   C．was happened   D．had happened 答案：A 解析: 略向含有Fe3+、Fe2+、Mg2+、的水溶液中，加入足量的Na2O2固体，充分反应后再加入过量的稀盐酸，上述离子数目没有明显变化的是（ ）A．Fe2+B．C．Fe3+D．Mg2+