Which of the following chemical equations show oxidation-reduction reactions?
a. Mg (s) + I₂ (aq) ⟶MgI₂ (s)
b. Pb(ClO₄)² (aq) + 2KI (aq) ⟶PbI₂ (s) + 2NaClO₄ (aq)
c. Fe₂O₃ (s) + 3CO (g) ⟶2Fe (s) + 3CO₂ (g)