A disproportionation reaction is one where the same element is simultaneously oxidized and reduced. (a) $Cu^+$ ($+1$) goes to $Cu^{2+}$ ($+2$, oxidation) and $Cu^0$ ($0$, reduction). (b) $Mn$ in $MnO_4^{2-}$ ($+6$) goes to $MnO_4^-$ ($+7$, oxidation) and $MnO_2$ ($+4$, reduction). (c) $KMnO_4$ decomposition is not disproportionation. (d) $Mn$ in $MnO_4^-$ ($+7$) and $Mn^{2+}$ ($+2$) both go to $MnO_2$ ($+4$), which is comproportionation.