The correct answer is C. Ethanol.
A carbonyl group is a functional group with the formula $R-CO-R’$, where $R$ and $R’$ can be alkyl groups, hydrogen atoms, or other substituents. It is a common functional group in organic chemistry and is found in many important compounds, including ketones, aldehydes, and carboxylic acids.
Ethanol is a simple alcohol with the formula $C_2H_6O$. It is a colorless, flammable liquid that is commonly used as a solvent and fuel. Ethanol does not contain a carbonyl group, as it does not have a carbon atom double-bonded to an oxygen atom.
Ketones are organic compounds that contain a carbonyl group attached to two alkyl groups. The general formula for a ketone is $R_2CO$. Ketones are found in many natural products, including ketone bodies, which are produced by the body during starvation or exercise.
Aldehydes are organic compounds that contain a carbonyl group attached to one alkyl group and one hydrogen atom. The general formula for an aldehyde is $RCHO$. Aldehydes are found in many natural products, including formaldehyde, which is used in embalming fluid.
Carboxylic acids are organic compounds that contain a carbonyl group attached to a hydroxyl group. The general formula for a carboxylic acid is $R-COOH$. Carboxylic acids are found in many natural products, including acetic acid, which is the main component of vinegar.