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': 'In epidemic, 1st step is: \nSelect and explain. \nA. Verification of diagnosis, B. Isolation, C. Immunization, D. Notification', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Verification of diagnosis', 'role': 'assistant'}]