The correct option is D Glycine
Essential amino acids are those amino acids that cannot be synthesized by the human body. Glycine is not an essential amino acid.
The nine essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. All other amino acids can be synthesized by the body itself and therefore are not required in the diet.