MnO₂和锌是制造干电池的主要原料

电解法生产MnO₂传统的工艺主要流程为：软锰矿加煤还原焙烧；用硫酸浸出焙烧料；浸出液（主要含Mn²⁺）经净化后再进行电解，MnO₂在电解池的阳极析出．

90年代后期发明了生产MnO₂和锌的新工艺，主要是采用软锰矿（主要成分为MnO₂，含少量Al₂O₃和SiO₂杂质）和闪锌矿（主要成分为ZnS，含少量FeS、CuS、CdS杂质）为主要原料，经过除杂后，得到含Zn²⁺、Mn²⁺离子的溶液，再通过电解同时获得MnO₂和锌．简化流程框图如下（中间产物的固体部分已经略去）：

软锰矿、闪锌矿 滤液A Zn²⁺、Mn²⁺、Fe²⁺、Al³⁺ ZnSO₄、MnSO₄溶液 Zn+MnO₂+产品D

已知各种金属离子完全沉淀的pH如下表：

回答下列问题：

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已知点A（2a+1，5a﹣2）在第一、三象限的角平分线上，点B（2m+7，m﹣1）在二、四象限的角平分线上，则（　　）