This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biostatistics, Subject name: Social & Preventive Medicine
[{'content': 'Best for studying the decline in percentage of syphilis in men and women in last 10 years \nSelect and explain. \nA. Pie cha, B. Histogram, C. Frequency polygon curve, D. Line diagram', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ref:Park's Textbook of Preventive and Social Medicine 25th Ed", 'role': 'assistant'}]