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: Medicine
[{'content': 'The normal time required to culture mycobacterium TB is : \nSelect and explain. \nA. 4-8 weeks, B. 2-3 weeks, C. 6-10 weeks, D. 21 days', 'role': 'user'}, {'content': 'Answer: A \nExplanation: M. tuberculosis 4-8 weeks is required before growth is detected. New methods have decreased the time required for bacteriologic confirmation of TB to 2-3 weeks. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 1350', 'role': 'assistant'}]