Question

what is the name of the functional group shown in the image? hydroxyl carboxyl aldehyde ketone carbonyl

Explanation:

The functional - group in the image has a carbon double - bonded to an oxygen ($C = O$) and also bonded to a hydroxyl group ($-OH$). This is the characteristic structure of a carboxyl group. Hydroxyl is $-OH$, aldehyde is $R - CHO$, ketone is $R - CO - R'$, and carbonyl is just the $C = O$ moiety. The carboxyl group is written as $-COOH$.

Answer:

B. carboxyl