Which of the following represents an oxidation-reduction reaction?
I. PCl3 (aq) + Cl2 (g) → PCl5 (aq)
II. 2 AgNO3 (aq) + Cu (s) → Cu(NO3)2 (aq) + 2 Ag (s)
III. CO2 (g) + 2 LiOH (aq) → Li2CO3 (aq) + H2O (l)
IV. FeCl2 (aq) + 2 NaOH (aq) → Fe(OH)2 (aq) + 2 NaCl (aq)