Step 1: Recall common functional groups. \( -CHO \): Aldehyde
\( -COOH \): Carboxylic acid
\( -C=O \): Carbonyl group (ketone or aldehyde)
\( -OH \): Hydroxyl group (alcohol or phenol)
Step 2: Identify the functional group of carboxylic acids. Carboxylic acids are characterized by the presence of the \( -COOH \) functional group (carboxyl group).