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
Deficiency of which vitamin causes excretion of xantheurenic acid in urine ? 
Select and explain. 
A. Folic acid, B. Pyridoxin, C. Niacin, D. Vitamin B12
B: Pyridoxin
Answer: B: Pyridoxin 
Explanation: Ans. is 'b' i.e., Pyridoxin