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
Amino acid with double chiral is ? 
Select and explain. 
A. Phenyalanine, B. Threonine, C. Tryptophane, D. Tyrosine
B: Threonine
Answer: B: Threonine 
Explanation: Ans. is 'b' i.e., Threonine