Identifying Functional Groups Involved in Acid-Base Reactions

In organic chemistry, various functional groups determine the properties and reactivity of organic molecules. A functional group is a specific group of atoms within a molecule that is responsible for certain characteristic chemical reactions of that molecule. For example, the hydroxyl group (-OH) is known for making compounds more polar and capable of hydrogen bonding.

Consider the following organic compounds:

1. Compound A: C₃H₈O, containing a hydroxyl (-OH) group
2. Compound B: C₅H₁₀O₂, containing a carboxylic acid (-COOH) group
3. Compound C: C₄H₁₀N, containing an amino (-NH₂) group
4. Compound D: C₂H₄, an alkene with no functional groups

Based on this information, which compound contains a functional group that is primarily involved in acid-base reactions?