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

Question

$\begin {array} {1 1} (1)\; Ag^{2+}\: (aq)\: +\: Ag(s) \: \longrightarrow \: 2\: Ag^+\: (aq) \\ (2)\;P_4(s)+\: 3\: OH^-(aq)+3\: H_2O \longrightarrow\: PH_3(g)\: + 3\: H_2P_2^-\: (aq) \\ (3)\;S(s)+O_2(g) \: \longrightarrow \: SO_2(g)  \\ (4)\;Zn(s) \: +\: CuSO_4\: (aq) \: \longrightarrow\: ZnSO_4 \: (aq)\: Cu(s) \end {array}$