The answer is: B. 2-methylpentan-2-ol.
A functional group is a group of atoms that determines many of the properties of an organic molecule.
Functional group for alcohol is hydroxyl group or hydroxy group (-OH).
Methyl group (-CH₃) is attached to second carbon atom of pentanol, that i why the name is 2-methyl.
Hydroxy group (-OH) is attached to second carbon atom of pentanol, that i why the name is 2-pentanol.