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

A

(a), (b) and (c)

B

(a), (c) and (d)

C

(a) and (d) only

D

(a) and (b) only