The correct option is B n-Octane
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.
Higher molecular mass molecules have higher boiling point than the lower mass molecules.
All have the same number molecular mass. n-Octane is a straight-chain compound that has a large suface area. So, there are more van der Waals forces of attaraction resulting in a high boiling point.