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: Microbiology
[{'content': 'In a patient only anti HBs Ag is positive in serum, all other markers are negative. This indicates ? \nSelect and explain. \nA. Acute hepatitis, B. Chronic active hepatitis, C. Persistent carrier, D. Hepatitis B vaccination', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Hepatitis B vaccination", 'role': 'assistant'}]