Which of the following reactions are disproportionation reaction? a)\(2Cu^{+}\rightarrow Cu^{2+}+Cu^{0}\) \(b)3MnO_4^{2-}+4H^{+} \rightarrow2MnO_4^{-}+MnO_2+2H_2O\) \(c)2KMnO_4\frac{\Delta}{\rightarrow}K_2MnO_4+MnO_2+O_2\) \(d)2MnO_4^{-}+3Mn^{2+}+2H_2O \rightarrow 5MnO_2+4H^\oplus\) Select the correct option from the following: