Which of the following is an oxidation-reduction reaction?
1) NaCl(aq) + AgNO₃(aq) → AgCl(s) + NaNO₃(aq)
2) hi(aq) + NaOH(aq) → nai(aq) + H₂O(l)
3) Pb(C₂H₃O₂)₂(aq) + 2 kcl(aq) → pbCl₂(s) + 2 kc2h3o2(aq)
4) 2 hi(aq) + ba(s) → BaI₂(aq) + h2(g)
5) All of the above are oxidation-reduction reactions.