Aspirin, also known as acetylsalicylic acid, contains two main functional groups: a carboxylic acid and an ester.
The carboxylic acid group (-COOH) is responsible for the acidic properties of aspirin, while the ester group (-COO-) is formed from the reaction between the acetic acid and the salicylic acid.
Therefore, the correct answer is b) carboxylic acid and ester.