True about Mantoux test:

Ans. is 'c' i.e., Usually read after 48-72 hoursConsidering other choices:(a) >10 mm is positive and 6-9 mm is Equivocal/Doubtful reaction.(b) It becomes positive after exposure to mycobacterium tuberculosis protein either in the form of infection or immunization and remains positive even after treatment.Note - Tuberculin test in Adults is used as Epidemiological marker and in Children is used as diagnostic marker.