Answer
The correct option is (c) R group.
Work Step by Step
All amino acids have a carbon atom attached to a hydrogen atom, amine group, carboxylic group and a side chain. The side chain is referred to as specific to an amino acid. The amine group, hydrogen atom, carboxylic group are common to all amino acids and they differ only in the R group. Therefore, the options (a), (b), (d), and (e) are incorrect. Different amino acids have different R groups. Peptide bond is formed when two amino acids join to form a polypeptide chain. Hence, the correct option is (c) R group.
