Answer:
b. Proteins
Explanation:
Amino acids are the substances that are bonded together in a specific sequence to make the polypeptide chains of proteins. All the 20 standard amino acids share a basic structure. All of them have a central carbon atom to which four functional groups are bonded. Three functional groups are common to all these amino acids. These common groups are carboxylic group, amino group (NH2) and a hydrogen atom. Therefore, all the proteins have "N" atoms in their structure. The last functional group is called the "side chain" that varies among different amino acids.
