题目

某溶液中大量存在四种离子：NO-3、SO2-4、H+、M，其物质的量之比为：N(NO-3):n(SO2-4):n(H+):n(M)=3:1:3:1，则M可能为                                          （    ）①Fe2+                                                                 ②Mg2+                                                 ③Cl—                                                     ④Ba2+A．①②④                          B．③                          C．②                          D．①②  答案：C解析:略 

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