This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
[{'content': 'Disease elimination is helped by \nSelect and explain. \nA. Herd immunity, B. Isolation, C. Quarantine, D. None', 'role': 'user'}, {'content': "Answer: A \nExplanation: If herd immunity is sufficiently high and it's level is maintained and stepped up by an ongoing immunization programme to the point where the susceptible persons are reduced to a small propoion of population it may lead to the elimination of disease in due course. Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 111", 'role': 'assistant'}]