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
Population pyramid is an example of: 
Select and explain. 
A. Histogram, B. Polygon, C. Pie diagram, D. Bar diagram
D: Bar diagram
Answer: D: Bar diagram 
Explanation: 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