Final answer:
The chemical equations that depict an oxidation-reduction reaction are generally characterized by the change in oxidation states of elements. The valid equation for an oxidation-reduction reaction is (a), which shows the reaction between oxygen and hydrogen to form water.
Step-by-step explanation:
The chemical equations that show an oxidation-reduction reaction are those in which the oxidation state of elements changes from the reactant side to the product side. These reactions involve a transfer of electrons between substances, where one substance gains electrons (reduction) and another loses electrons (oxidation). (a) O₂ + 2H₂ → 2H₂O - This is an oxidation-reduction reaction because hydrogen is being oxidized and oxygen is being reduced. (c) 2Al + 6H₂ → 2AlI₃ + 3H₂ - The reaction listed contains a typo and thus cannot be accurately assessed for being an oxidation-reduction reaction.
Other given chemical equations either do not show changes in oxidation states or are not complete or correct representations for oxidation-reduction reactions. For example, equation (c) seems to contain typos and is not a valid chemical equation. Part (b) represents a double displacement reaction, not an oxidation-reduction reaction. The unlisted equation involving Silver (Ag), based on the oxidation state change during the reaction, would indicate an oxidation-reduction process. So, the valid equation for an oxidation-reduction reaction is (a), which shows the reaction between oxygen and hydrogen to form water.