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': 'Deficiency of which vitamin causes excretion of xantheurenic acid in urine ? \nSelect and explain. \nA. Folic acid, B. Pyridoxin, C. Niacin, D. Vitamin B12', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Pyridoxin", 'role': 'assistant'}]