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': 'Not true about Montoux test \nSelect and explain. \nA. PPD RT-23 with tween 80 used as strain, B. Result is seen after 3 weeks, C. > 9mm induration is taken as positive, D. Type IV Hypersensitivity', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]