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': 'Gastrectomy produces deficiency of which vitamin ? \nSelect and explain. \nA. Vitamin B6, B. Vitamin B12, C. Vitamin B2, D. Vitamin B1', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Vitamin B12", 'role': 'assistant'}]