When potassium permanganate, $KMn{O}_4$, is added to an acidified solution of oxalic acid, $H_2{C}_2{O}_4$, the products are $C{O}_2$ gas and $M{n}^{\mathit{2}\mathit{+}}$ ions. What is the reducing agent in this reaction?

When potassium permanganate, $KMn{O}_4$, is added to an acidified solution of oxalic acid, $H_2{C}_2{O}_4$, the products are $C{O}_2$ gas and $M{n}^{\mathit{2}\mathit{+}}$ ions. $H_2{C}_2{O}_4$ is the reducing agent in this reaction.

The reaction is having follows,

Oxidation: ${\mathrm{H}}_2{\mathrm{C}}_2{\mathrm{O}}_4 \to {\mathrm{Co}}_2$

                        +3              +4

Reduction: ${\mathrm{MnO}}_4^{-} \to {\mathrm{Mn}}^{2+}$

                       +7                 +2

Hence, option B is correct.