A nurse is caring for a client who has a history of exposure to TB and symptoms of night sweats and hemoptysis. Which of the following tests should the nurse realize is the most reliable to confirm the diagnosis of active pulmonary TB?

A. A sputum culture for acid-fast bacillus (AFB) is the most reliable test to confirm active pulmonary tuberculosis, as it identifies the presence of Mycobacterium tuberculosis and allows for drug sensitivity testing. B. A sputum smear can provide rapid preliminary results but is less sensitive and specific than a culture. C. The Mantoux test (PPD) detects latent TB infection, not active disease, and can produce false positives in those vaccinated with BCG. D. A chest x-ray can show suggestive signs of TB but cannot confirm the diagnosis without microbiological evidence.