ASSERTION: n-Pentane and n-Hexane belong to a homologous series.
REASON: n-Pentane and n-Hexane belong to the same class of hydrocarbons and they differ by a - CH2 - group.
Both ASSERTION REASON are correct and REASON is the correct explanation for ASSERTION.
Here we have alkanes that differ by one - CH2 - (methylene) in molecular formula/weight. The subsequent homologues of alkanes differ by a - CH2 - . Thus the reason explains the assertion, which is true.
Hence, the answer is A