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': 'Epidemiologic study of Hepatitis B is - \nSelect and explain. \nA. HBe Ag, B. HBc Ag, C. HBs Ag is used, D. Anti HBc', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]