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': 'Number of center of excellance in vision 2020 - \nSelect and explain. \nA. 20, B. 200, C. 2000, D. 20000', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., 20", 'role': 'assistant'}]