In which of the following reactions heterogeneous catalysis involved ?
(i) 2SO2(g) + O2(g)→2SO2(g)
(ii) 2SO2(g)→2SO3(g)
(iii) N2(g) + 3H2(g)→2NH3(g)
(iv) CH3COOCH3(l) + H2O(l) HCI → CH3COOH(aq) + CH3OH(aq)
(a) (ii), (iii)
(b) (ii), (iii), (iv)
(c) (i), (ii), (iii)
(d) (iv)