This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Demography, Subject name: Social & Preventive Medicine
[{'content': 'Growth rate is calculated by? \nSelect and explain. \nA. Crude birth rate/Crude death rate, B. Net reproduction--Crude death rate, C. Total fertility rate--Crude death rat, D. Crude birth rate - Crude death rate', 'role': 'user'}, {'content': 'Answer: D \nExplanation: ANSWER: (D) Crude birth rate - Crude death rateREF: Park 20th ed p. 412When crude death rate is substracted from crude birth rate, the net residual is the annual growth rate, exclusive of migration.Relation between growth rate and populationRatingAnnual rate of growth %Number of years required for population to double itselfStationary populationNo growth Slow growth<0.5>139Moderate growth0.5 -1.070-139Rapid growth1.0-1.547-70Very rapid growth1.5-2.035-47Explosive growth2.0-2.528-35 2.5-3.023-28 3.0-3.520-23 3.5-4.018-20', 'role': 'assistant'}]