The formula for Iron oxide is Fe2O3. The symbols of iron and oxygen are Fe and O respectively. The valency of Iron in Ferric oxide is +3 while in Ferrous oxide is +2. On the other hand, the valency of Oxygen is -2. Putting the valency of Iron under oxygen and putting the valency of oxygen under Iron, makes the complete formula of Iron oxide.
The oxidation number for Oxygen is -2. Fe is a transition metal so it does its oxidation number is dynamic. In order for the compound to be neutral, two negative charges for Oxygen would be equivalent to two positive charges from Fe so none of the above answers are correct. I am not sure of the answer actually...