This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Classification and metabolism of amino acids, Subject name: Biochemistry
Non-essential amino acid : 
Select and explain. 
A. Tryptophan, B. Tyrosine, C. Arginine, D. Histidine
B: Tyrosine
Answer: B: Tyrosine 
Explanation: Essential amino acids are those which can't be synthesised in the body and must be taken in the diet. Alanine can be synthesized from pyruvate by transamination in a single step. So, alanine is not a dietarily essential amino acid. Semi-essential amino acids: Those which can be synthesized in body but to some extent.