Indicate whether the following balanced equations involve oxidation-reduction. If they do, identify the elements that undergo changes

Question:

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