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
[{'content': 'Non- essential amino acid \nSelect and explain. \nA. Valine, B. Leucine, C. Tryptophan, D. Serine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]