(i) $\mathrm{CO}\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right) \stackrel{\mathrm{Ni}\left(\mathrm{s}\right)}{\to } {\mathrm{CH}}_4\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$
(ii) $\mathrm{CO}\left(\mathrm{g}\right)+2{\mathrm{H}}_2\left(\mathrm{g}\right) \stackrel{\mathrm{Cu}/\mathrm{ZnO}-{\mathrm{Cr}}_2{\mathrm{O}}_3}{\to } {\mathrm{CH}}_3\mathrm{OH}\left(\mathrm{g}\right)$
(iii) $\mathrm{CO}\left(\mathrm{g}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right) \stackrel{\mathrm{Cu}}{\to } \mathrm{HCHO}\left(\mathrm{g}\right)$
Which of the above reactions is/are a catalytic reaction?

$\mathrm{CO}\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right) \stackrel{\mathrm{Ni}}{\to } {\mathrm{CH}}_4\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$
$\mathrm{CO}\left(\mathrm{g}\right)+2{\mathrm{H}}_2\left(\mathrm{g}\right) \stackrel{\mathrm{Cu}/\mathrm{ZnO}-{\mathrm{Cr}}_2{\mathrm{O}}_3}{\to } {\mathrm{CH}}_3\mathrm{OH}\left(\mathrm{g}\right)$
$\mathrm{CO}\left(\mathrm{g}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right) \stackrel{\mathrm{Cu}\left(\mathrm{s}\right)}{\to }\mathrm{HCHO}\left(\mathrm{g}\right)$
Here, Ni, Cu/ZnO-Cr₂O₃ and Cu are catalysts.
Different catalysts act on same reactants give different products.