Answer
(b) an amino acid
Work Step by Step
All amino acids include an amine group and an organic acid group, allowing them to act as either an acid or a base. Proteins are composed of many amino acids that are joined together by peptide bonds. Because there are no peptide bonds in the described molecule, it cannot be a protein. Monosaccharides and fats are composed of very different molecular groups and have very different structures from the one described in the question.
