Which one of the following is an example for homogeneous catalysis?

In homogeneous catalysis, reactants and catalyst are in the same phase.
(a) \(\mathrm{SO}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \stackrel{\mathrm{Pt}(\mathrm{s})}{\rightleftharpoons} \mathrm{SO}_{3}(\mathrm{~g})\)
(Contact process)
It is an example of heterogeneous catalysis.
(b) \(\mathrm{N}_{2}(\mathrm{~g})+\mathrm{H}_{2}(\mathrm{~g}) \stackrel{\mathrm{Fe}(\mathrm{s})}{\rightleftharpoons} 2 \mathrm{NH}_{3}(\mathrm{~g})\)
(Haber's process)
It is an example of heterogeneous catalysis.
(c) \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{aq}) \stackrel{\mathrm{HCl}(\mathrm{aq})}{\rightleftharpoons} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\) \(+\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\) It is an example of homogeneous catalysis.
(d)


Thus, it is also an example of heterogeneous catalysis.