Among the following, select the disproportionation reaction?
i) $2\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\to 2\mathrm{PbO}+4{\mathrm{NO}}_2+{\mathrm{O}}_2$      ii) ${\mathrm{I}}_2\to {\mathrm{I}}^{-}+{\mathrm{IO}}_3^{-}$
iii) $3{\mathrm{CI}}_2+6\mathrm{NaOH}\to 5\mathrm{NaCI}+{\mathrm{NaCIO}}_3+3{\mathrm{H}}_2\mathrm{O}$
iv) ${\mathrm{P}}_4+3\mathrm{NaOH}+3{\mathrm{H}}_2\mathrm{O}\to 3{\mathrm{NaH}}_2{\mathrm{PO}}_2+{\mathrm{PH}}_3$