This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the following is an optically inactive amino acid? 
Select and explain. 
A. Threonine, B. Tyrosine, C. Glycine, D. Serine
C: Glycine
Answer: C: Glycine 
Explanation: Optical properties: All the amino acids except glycine possess optical isomers due to the presence of asymmetric carbon atom.
Ref: Satyanarayan 3rd edition page no: 49