Question

part a
a hydroxyl group is
also called a carbonyl group.
characteristic of proteins.
composed of two oxygen atoms.
characteristic of alcohols.

Explanation:

A hydroxyl group (-OH) is characteristic of alcohols. A carbonyl group is C=O, different from -OH. Proteins have functional groups like amino and carboxyl, not mainly hydroxyl. A hydroxyl group has one oxygen and one hydrogen atom, not two oxygen atoms.

Answer:

D. characteristic of alcohols