Which one of the following is an example of disproportionation reaction ?
$3MnO_4^{2 - } + 4{H^ + } \to 2MnO_4^ - + Mn{O_2} + 2{H_2}O$
$MnO_4^ - + 4{H^ + } + 4{e^ - } \to Mn{O_2} + 2{H_2}O$
$10{I^ - } + 2MnO_4^ - + 16{H^ + } \to 2M{n^{2 + }} + 8{H_2}O + 5{I_2}$
$8MnO_4^ - + 3{S_2}O_3^{2 - } + {H_2}O \to 8Mn{O_2} + 6SO_4^{2 - } + 2O{H^ - }$
