This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
[{'content': 'Tuberculin test denotes: \nSelect and explain. \nA. Previous or present sensitivity to tubercle proteins, B. Patient is resistant to TB, C. Person is susceptible to TB, D. Protective immune status of individual against TB', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Previous or present sensitivity to tubercle proteins(a) Tuberculin test denotes Type IV (delayed) hypersensitivity to tuberculoprotein 0.1 ml (Purified protein derivative) and used in diagnosis of latent tuberculosis.(b) Positive tuberculin test indicates exposure to Mycobacterium tuberculosis in the form of infection or immunization with or without active disease.", 'role': 'assistant'}]