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

Question

( A ) (a), (b) and (c)
( B ) (a) and (b) only
( C ) (a), (c) and (d)
( D ) (a) and (d) only