Among the given compounds, ethanol C2H5−OH has the highest boiling point due to intermolecular hydrogen bonding. Usually, alcohols have higher boiling points than alkyl halides, alkanes, and ketones of comparable molar mass.
This is due to the fact that alcohol can form intermolecular hydrogen bonds. This leads to the molecular association. Energy is required to break inter-molecular hydrogen bonds. This increases the boiling points.
Therefore, the correct option is A