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': 'After vaccination against Japanese encephalitis immunity developes in - \nSelect and explain. \nA. 30 days, B. 7 days, C. 10 days, D. 21 days', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]