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: Dental
[{'content': 'Contraction of Demographic-Gap starts in: \nSelect and explain. \nA. Stage I, B. Late Stage II, C. Early Stage III, D. Stage IV', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Demographic Cycle and Concepts\n\nDemographic cycle is closely related to: Socio-economic progress of a country\n5 stages (phases) of demographic cycle through which a nation passes', 'role': 'assistant'}]