The correct option is C 6
Tripeptides are amino acids polymers in which three individual amino acid units, called residues, are linked together by amide bonds. In these, an amine group from one residue forms ad amide bond with the carboxyl group of a second residue, the amino group of the second forms and amide bond with the carboxyl group of the third. Therefore, glycine (NH2−CH2−COOH)alanine(CH3−CH−COOH|NH2) and phenyl C6H5−CH2−CHCOOH|NH2 can be linked in Six different ways.