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': 'Population pyramid is an example of: \nSelect and explain. \nA. Histogram, B. Polygon, C. Pie diagram, D. Bar diagram', 'role': 'user'}, {'content': 'Answer: D \nExplanation: A variant of bar diagram is population pyramid. It is used in demography and shows the age-sex distribution of a population. Ref: Medical biostatistics, 1st edition pg: 137', 'role': 'assistant'}]