Final answer:
In an oxidation reaction involving ClO2, the oxidation state of chlorine must increase. ClO3- and ClO4- are possible products because they have chlorine in higher oxidation states of +5 and +7 respectively, while ClO, Cl2, and Cl- have lower oxidation states.
Step-by-step explanation:
The question requires understanding the change in oxidation numbers of a ClO2 molecule during an oxidation reaction. Oxidation involves the increase in oxidation number. In ClO2, chlorine has an oxidation state of +4. For it to undergo oxidation, it must form a product with chlorine at a higher oxidation state.
Among the listed species, ClO3- and ClO4- have chlorine in the oxidation states of +5 and +7, respectively. Therefore, both of these could be products of an oxidation reaction of ClO2. However, ClO (with chlorine at +1), Cl2 (with chlorine at 0), and Cl- (with chlorine at -1) cannot be products of the oxidation of ClO2 since their oxidation states are lower than +4.