Indicate whether the following balanced equations involve oxidation-reduction. If they do, identify the elements that undergo changes in oxidation number.
(a)PBr3(l) +3H2O(l)=H3PO3(aq) + 3HBr(aq)
(b)NaI(aq) + 3HOCl(aq)=NaIO3(aq) + HCl(aq)
(c)3SO2(g) + 2HNO3(aq) + 2H2O(l)=3H2SO4(aq) + 2NO(g)
(d) 2H2SO4(aq) + 2NaBr(s)=Br2(l) + SO2(g) + Na2SO4(aq) + 2H2O(l)