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

Which of the following reactions are disproportionation reactions?
$(a)$ $2 Cu^{+} \rightarrow Cu^{2+} + Cu^{0}$
$(b)$ $3 MnO_{4}^{2-} + 4 H^{+} \rightarrow 2 MnO_{4}^{-} + MnO_{2} + 2 H_{2}O$
$(c)$ $2 KMnO_{4} \xrightarrow{\Delta} K_{2}MnO_{4} + MnO_{2} + O_{2}$
$(d)$ $2 MnO_{4}^{-} + 3 Mn^{2+} + 2 H_{2}O \rightarrow 5 MnO_{2} + 4 H^{+}$
Select the correct option from the following:

Assign $A$,$B$,$C$,$D$ from the given type of reaction.
$P_4 + 3NaOH + 3H_2O \longrightarrow PH_3 + 3NaH_2PO_2$
(Note: The reaction provided is the standard balanced equation for the disproportionation of white phosphorus.)

Assign $A, B, C, D$ from the given type of reaction.
$Cl_2 + 2NaOH \longrightarrow NaCl + NaOCl + H_2O$

For the reaction,$NH_4NO_2 \rightarrow N_2 + 2H_2O$,which of the following phenomena is true regarding nitrogen?

$Cu^{+}$ ion is not stable in aqueous solution,because it shows $-$