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.