The correct option is D 2-methylpentane > 2,3-dimethylbutane > 2,2-dimethylbutane
Boiling point in alkane depends upon the chains of atoms and the molecular mass of the molecules. Straight-chain molecules have higher boiling point than the branched-chain compounds.
Among given compounds, 2-methylpentane has the least number of branches thus it has the highest boiling point.
For the same molar mass, as branching decreases, the overall surface area increases. This leads to a reduction in the intermolecular forces, thereby decreasing boiling point.
so between 2,3-dimethylbutane and 2,2-dimethylbutane, 2,2-dimethylbutane is more branched and has large surface area thus it lower boiling point than 2,3-dimethylbutane.
Further, the boiling point of these compounds follows the order : 2-methylpentane > 2,3-dimethylbutane > 2,2-dimethylbutane.