错误:
K2S %2B K2MnO4 %2B H2O %3D MnO%28OH%292 %2B S %2B KOH
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不需要的字符 ('%')K2S %2B K2MnO4 %2B H2O %3D MnO%28OH%292 %2B S %2B KOH
^
不需要的字符 ('%')