. Carboxylic Acid Explanation: Alkenes are hydrocarbons with at least one double bond between carbon atoms.e.g CH2=CH2. Alcohols have the funtional group -OH but no C=O bond e.g C2H5OH. Ketones have a -C=O attached to an alkyl group on both ends e.g CH3COCH3. CH3COOH has a -C=O as well as an -OH group i.e. -COOH is the functional group of a Carboxylic Acid. So the Answer is B. Ch3COOH, known as acetic acid, is an organic compound from the homologous series of Carboxylic acids. The functional group of Carboxylic acids is -COOH group. It is a colourless liquid that is acidic in nature. It's IUPAC name is Ethanoic acid, where ethan- comes from the presence of 2 Carbons in the compound and the suffix "-oic acid" is from the series it belongs to.