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': 'A total of 3500 patient with thyroid cancer are identified and surveyed by patient interviews with reference to past exposure to radiation. The study design most appropriately illustrates - \nSelect and explain. \nA. Case series report, B. Case control study, C. Case report, D. Clinical trial', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]