The correct option is A 14
Compounds having the same functional group as well as chemical characteristics form a homologous series. The members of a homologous series are called homologues.
The successive members of a homologous series are differ by a -CH2 group. The molecular mass of a -CH2 group is 14 amu. Hence, each successive homologue of a homologous series differ by a mass of 14 amu.