Which of the following is an oxidation-reduction reaction? ZnS(s) + 2O2(g) mc011-1.jpg ZnSO4(s) CaO(s) + H2O(l) mc011-2.jpg Ca(OH)2(s) 6Li2O(s) + P4O10(g) mc011-3.jpg 4Li3PO4(s) SO2(g) + H2O(l) mc011-4.jpg H2SO3(aq)