The correct option is B Proteins
Proteins are the building blocks, which takes part in several metabolic reaction. They have four different levels of structure primary, secondary, tertiary and quaternary. There are 20 different standard L-α-amino acids used by cells for protein construction. Amino acids contain both a basic amino group and an acidic carboxyl group. This difunctionality allows the individual amino acids to join together in long chains by forming peptide bonds: amide bonds between the -NH2 of one amino acid and the -COOH of another. Sequences with fewer than 50 amino acids are generally referred to as peptides, while the terms protein or polypeptide are used for longer sequences. A protein can be made up of one or more polypeptide molecules. The end of the peptide or protein sequence with a free carboxyl group is called the carboxy-terminus or C-terminus. The terms amino-terminus or N-terminus describe the end of the sequence with a free α-amino group. The amino acids differ in structure by the substituent on their side chains. These side chains confer different chemical, physical and structural properties to the final peptide or protein.
So, the correct answer is option B.