Answer:
The answer to your question is: letter B.
Step-by-step 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)