Within organic chemistry, functional groups play a critical role in determining the properties and reactions of molecules. A functional group is a specific group of atoms within a molecule that is responsible for its characteristic chemical reactions. For example, a hydroxyl group (-OH) is recognized as the functional group for alcohols.

In this question, you are asked to identify the functional group present in the molecule propanoic acid (C₂H₅COOH). Which functional group does propanoic acid contain?