Which diagnostic test is the most definitive test used to detect meningitis?

A. CBC: A CBC can indicate infection (elevated white blood cell count), but it is not specific for meningitis. B. Urinalysis: Urinalysis is not relevant for diagnosing meningitis. C. CT scan: A CT scan can detect complications like increased intracranial pressure but does not diagnose meningitis directly. D. Lumbar puncture: A lumbar puncture allows direct analysis of CSF for glucose, protein, white blood cells, and organisms, which is definitive for diagnosing meningitis.