IMAT 2012 Q61 [Oxidising Agents]

In the following reactions, which substances are acting as oxidising agents?

{C(s) + O_2(g) → CO_2(g)}

{2Fe^{3+}(aq) + 2I­^{-}(aq) → Fe^{2+}(aq) + I_2(aq)}

{Mg(s) + 2H^+(aq) → Mg^{2+}(aq) + H_2(g)}

A. {C(s), Fe^{3+}(aq), H^{+}(aq)}
B. {C(s), Fe^{3+}(aq), Mg(s)}
C. {O_2(g), I­(aq), H^+(aq)}
D.{ O_2(g), Fe^{3+}(aq), H^+(aq)}
E. {O_2(g), I­^{-}(aq), Mg(s)}