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: Social & Preventive Medicine
[{'content': 'Vitamin synthesized by bacteria in the intestine is: March 2004 \nSelect and explain. \nA. Vitamin K, B. Vitamin B1, C. Vitamin D, D. Biotin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A i.e. Vitamin K', 'role': 'assistant'}]