Which one of the following is an example of disproportionation reaction?

$\displaystyle 3 \mathrm{MnO}_4^{2-}+4 \mathrm{H}^{+} \rightarrow 2 \mathrm{MnO}_4^{-}+\mathrm{MnO}_2+2 \mathrm{H}_2 \mathrm{O}$

$\displaystyle \mathrm{MnO}_4^{-}+4 \mathrm{H}^{+}+4 e^{-} \rightarrow \mathrm{MnO}_2+2 \mathrm{H}_2 \mathrm{O}$

$\displaystyle 10 \mathrm{I}^{-}+2 \mathrm{MnO}_4^{-}+16 \mathrm{H}^{+} \rightarrow 2 \mathrm{Mn}^{2+}+8 \mathrm{H}_2 \mathrm{O}+5 \mathrm{I}_2$

$\displaystyle 8 \mathrm{MnO}_4^{-}+3 \mathrm{~S}_2 \mathrm{O}_3^{2-}+\mathrm{H}_2 \mathrm{O} \rightarrow 8 \mathrm{MnO}_2+6 \mathrm{SO}_4^{2-}+2 \mathrm{OH}^{-}$