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': 'Following is a non-essential amino acid: \nSelect and explain. \nA. Phenylalanine, B. Proline, C. Tryptophan, D. Threonine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]