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