Which of the following functional groups comprises a carbon atom bonded to a hydroxyl group?

A. ester

B. alcohol

C. thiol

D. carbonyl

B. alcohol

Hydroxyl group is an - OH branch

so,

R - OH is alcohol

The correct option is: B. alcohol

Explanation:

A. ester (R-COOR') : In this functional group, the carbon atom forms a single bond with an alkoxy group and a double-bond with an oxygen atom.

B. alcohol (R-COH) : In this functional group, the carbon atom is bonded to a hydroxyl group.

C. thiol (R-SH) : In this functional group, the carbon atom is bonded to a thiol group.

D. carbonyl (R-COR') : In this functional group, the carbon atom forms a double-bond with an oxygen atom.

Therefore, alcohols are the class of organic molecules in which a carbon atom is bonded to a hydroxyl functional group.