This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
[{'content': 'The amino acid that can be converted into a vitamin is: \nSelect and explain. \nA. Glycine, B. Tryptophan, C. Phenylalanine, D. Lysine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B Harper, 26th ed. p. 258 & 25th ed, p. 630, Fig (52.4)', 'role': 'assistant'}]