In the following redox reaction, the reducing agent is MnO2 (option D). Details about reducing agent can be found below.
A reducing agent in a redox reaction is any substance that reduces, or donates electrons to another, hence, it becomes oxidized.
According to this question, a redox reaction is given as follows: MnO2(s) + 4H+(aq) + 2Cl–(aq) = Mn2+(aq) + 2H2O(l) + Cl2(g)
As shown in the equation, MnO2 is oxidized into Mn2+, therefore, it is the reducing agent.
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