The reaction in which atoms combine with unsaturated carbon compounds to form saturated carbon compounds is known as
Addition reaction
Different types of reactions are listed below:
(i) Substitution reaction: Reaction in which an atom or a group in a compound is replaced by another atom or a group.
(ii) Addition reaction: Reaction in which atoms combine with unsaturated carbon compounds to form saturated carbon compounds.
(iii) Polymerization: Process in which a large number of simple molecules combine to form the complex molecule.
(iv) Combustion reaction: Reaction in which hydrocarbons combine with oxygen to form carbon dioxide and water along with heat and light.
Therefore, the correct answer is an addition reaction.