Oils on treating with hydrogen in the presence of palladium or nickel catalyst form fats. This is an example of
(a) Addition reaction
(b) Substitution reaction
(c) Displacement reaction
(d) Oxidation reaction
Oils are unsaturated fatty acids and on treating them with hydrogen in the presence palladium or nickel, hydrogenation reaction takes place wherein H atoms are added over the double bonds. So oil is converted to fats i.e. saturated fatty acids. Therefore, the reaction is an addition reaction.
So, the correct answer is (a) addition reaction