What functional group consists of a carbon atom double-bonded to an oxygen atom?

carbohydrate group
carbonyl group
hydroxyl group
ketone group

The answer to your question is: letter B.

Explanation:

Carbon atom double-bonded to an oxygen atom    C= O,

a) Carbohydrate group   this group does not exist

b)Carbonyl group  This option is right, carbonyl group is C=O

c) Hydroxyl group  This option is incorrect, hydroxyl group is OH, very different from C=O

d) Ketone group Ketone group does not exist, ketones have the same functional group as aldehydes (C=O)

Carbonyl group

Explanation:

A carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom (presented as C ═ O). Ketones and aldehydes are examples of simple compounds that contain a carbonyl group.