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': 'The spindle-shaped Age pyramid denotes? \nSelect and explain. \nA. Developing country, B. Underdeveloped country, C. Middle east country, D. Developed country', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]