Which of the following functional groups represents an aldehyde?
Correct: C
A) -OH is the hydroxyl group, characteristic of alcohols. B) -COOH is the carboxyl group, characteristic of carboxylic acids. C) -CHO is the formyl group, characteristic of aldehydes, where the carbon atom is double-bonded to oxygen and single-bonded to hydrogen. D) -CO- is the carbonyl group, which, when located between two alkyl groups, characterizes ketones.