For the redox reaction $\text{MnO}_4^- + \text{C}_2\text{O}_4^{2-} + \text{H}^+ \rightarrow \text{Mn}^{2+} + \text{CO}_2 + \text{H}_2\text{O}$. The correct coefficients of the reactants for the balanced equation are $\text{MnO}_4^-$, $\text{C}_2\text{O}_4^{2-}$, $\text{H}^+$ respectively:

The n-factor of $\text{MnO}_4^-$ is 5 and the n-factor of $\text{C}_2\text{O}_4^{2-}$ is 2. The ratio of n-factors is 5:2, so the molar ratio in the balanced reaction is 2:5. The balanced equation is $2\text{MnO}_4^- + 5\text{C}_2\text{O}_4^{2-} + 16\text{H}^+ \rightarrow 2\text{Mn}^{2+} + 10\text{CO}_2 + 8\text{H}_2\text{O}$.