In which of the following reactions heterogenous catalysis is involved?
(a) 2SO2 (g) + O2 (g) +NO(g)→ 2SO3 (g)
(b) 2SO2 (g) +Pt(s)→ 2SO3 (g)
(c) N2 (g) + 3H2 (g) +Fe(s)→ 2NH3 (g)
(d) CH3COOCH3 (l) + H2O (l) +HCl(l)→ CH3COOH (aq) + CH3OH (aq)
(i) (b), (c)
(ii) (b), (c), (d)
(iii) (a), (b), (c)
(iv) (d)