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': 'Under the RNTCP, sputum culture for MDR TB is to be examined for at least: \nSelect and explain. \nA. 4 weeks, B. 8 weeks, C. 10 weeks, D. 12 weeks', 'role': 'user'}, {'content': 'Answer: B \nExplanation: All cultures should be examined 48-72 hours after inoculation to detect gross contaminants. Thereafter cultures are examined weekly, up to 8 weeks on a specified day of the week. Ref:', 'role': 'assistant'}]