This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of protein and amino acid, Subject name: Biochemistry
The semi-essential amino acids are 
Select and explain. 
A. Phenylalanine, B. Lysine, C. Tryptophan, D. Arginine
D: Arginine
Answer: D: Arginine 
Explanation: Others are essential amino acids.Semi-essential amino acids are arginine and histidine only.Ref: DM Vasudevan - Textbook of Biochemistry for Medical Students, 7th edition, page no: 27