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': 'Example for multipurpose screening. \nSelect and explain. \nA. Chest X-ray for Tb on large population, B. Annual health check ups, C. Pap smear in elderly females, D. Eye check up in school children', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]