Concept:A homologous series is a family of organic compounds that share the same functional group, with each member differing from the next by a
−CH2​− unit.
Explanation:In a homologous series, the same functional group replaces hydrogen atoms on a carbon chain.
Each successive compound differs from the previous one by one
CH2​ group.
For example, the alkane series is
CH4​,
C2​H6​,
C3​H8​, and so on.
All members of a homologous series show similar chemical properties because their functional group is identical.
Their physical properties, such as boiling point and melting point, change gradually with increasing molecular mass.
Common examples are alkanes, alkenes, and alkynes.
Catenation refers to the self-linking of atoms of the same element to form chains.
Isomers are compounds with the same molecular formula but different structural arrangements.
Heterologous series is not a standard term used in organic chemistry.
Therefore, the correct answer is the homologous series.
Answer:Option D. homologous series