<prompt> Optically inactive amino acid isare:ThreonineThyronineValineGlycine  <response>: Ans: d. Glycine Amino acids having an asymmetric carbon atom exhibit optical activity. Asymmetry arises when 4 different groups are attached to the same carbon atomGlycine is the simplest amino acids has no asymmetric carbon atom therefore shows no optical activity. All others are optically activeThe mirror image forms produced with reference to the alpha carbon atom, are called D L isomersIsoleucine er threonine have 2 optically active centres therefore each has 4 diastereo isomers 