This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'Leprosy is not yet eradicated because - \nSelect and explain. \nA. No effective vaccine, B. Highly Infectious but low pathogenicity, C. Only humans are reservoir, D. Long incubation period', 'role': 'user'}, {'content': 'Answer: D \nExplanation: <p> Long incubation period (single best answer) Reference:Park&;s textbook of preventive and social medicine,K.Park,22nd edition,page no:291. <\\p>', 'role': 'assistant'}]