Classify the following as acid-base reactions or oxidation-reduction reactions: (a) Na2S(aq)+2HCl(aq)⟶2NaCl(aq)+H2S(g) (b) 2Na(s)+2HCl(aq)⟶2NaCl(aq)+H2(g) (c) Mg(s)+Cl2(g)⟶MgCl2(s) (d) MgO(s)+2HCl(aq)⟶MgCl2(aq)+H2O(l) (e) K3P(s)+2O2(g)⟶K3PO4(s) (f) 3KOH(aq)+H3PO4(aq)⟶K3PO4(aq)+3H2O(l)