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': 'A bacterium can divide every 20 minutes. Beginning with a single individual, how many bacteria will be there in the population if there is exponential growth for 3 hours? \nSelect and explain. \nA. 512, B. 440, C. 18, D. 1024', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A bacterium can divide every 20 minutes and exponential growth is for 3 hours,\nThus, C = 1,\nAnd r = 1 (it doubles every time)\nn = 3 hours/20 minutes = 9 times\nThus P = C (1 + r)n = 1 (1 + 1)9 = 29 = 512', 'role': 'assistant'}]