Concept:The parent chain is the longest continuous chain of carbon atoms in the molecule.Explanation:The structure is 2-methylbutanoic acid: HOOC−CH(CH3)−CH2−CH3.The longest continuous chain must include the carboxyl carbon of the −COOH group.This main chain has 4 carbon atoms, while the methyl group is a branch.Therefore, the parent chain contains 4 carbon atoms.Answer:The parent chain contains 4 carbon atoms. Correct option: B.
