This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Mycobacteria, Subject name: Microbiology
[{'content': 'Negative montoux test is when induration is - \nSelect and explain. \nA. <5mm, B. <10mm, C. <15 mm, D. <20 mm', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., < 5 mm MethodIntradermal injection of PPD on flexor aspect of forearm|Examined at 48-72 hours||||Induration > 10 mmInduration < 5 mmInduration 6-9 mm|||PositiveNegativeEquivocal|Repeat tuberculin test (two step testing)", 'role': 'assistant'}]