The correct answer is C. Aldehyde.
An aldehyde is a compound that contains the functional group -CHO. This functional group is a carbon atom double-bonded to an oxygen atom and single-bonded to a hydrogen atom. Aldehydes are found in many different compounds, including acetaldehyde, formaldehyde, and benzaldehyde.
Ketones are compounds that contain the functional group -CO-. This functional group is a carbon atom double-bonded to an oxygen atom. Ketones are found in many different compounds, including acetone, acetophenone, and benzophenone.
Alcohols are compounds that contain the functional group -OH. This functional group is a hydroxyl group, which is a hydrogen atom bonded to an oxygen atom. Alcohols are found in many different compounds, including ethanol, methanol, and isopropyl alcohol.
Carboxylic acids are compounds that contain the functional group -COOH. This functional group is a carboxyl group, which is a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group. Carboxylic acids are found in many different compounds, including acetic acid, formic acid, and benzoic acid.
In conclusion, the functional group -CHO is present in aldehydes.