ACS Gen Chem Practice Test 12

A proposed mechanism for the decomposition of hydrogen peroxide is

Step 1: ${\mathrm{H}}_2{\mathrm{O}}_2+{\mathrm{I}}^{-}\to {\mathrm{H}}_2\mathrm{O}+\mathrm{I}{\mathrm{O}}^{-}$ Step 2: ${\mathrm{H}}_2{\mathrm{O}}_2+\mathrm{I}{\mathrm{O}}^{-}\to {\mathrm{H}}_2\mathrm{O}+{\mathrm{O}}_2+{\mathrm{I}}^{-}$

Which statement correctly identifies the roles of ${\mathrm{I}}^{-}$ and $\mathrm{I}{\mathrm{O}}^{-}$?