Final answer:
The threshold for diagnosing pneumonia from a Bronchoalveolar Lavage (BAL) sample is typically a CFU count of less than 10^4 CFU/mL.
Step-by-step explanation:
The diagnosis of pneumonia is typically based on clinical signs and symptoms, along with the results of diagnostic tests, including bacterial cultures. In the case of bronchoalveolar lavage (BAL) samples, the number of Colony-Forming Units (CFUs) is used as an indicator of bacterial infection. The threshold for diagnosing pneumonia from a BAL sample is typically a CFU count of less than 10^4 CFU/mL, which means option b) <10^4 CFU/mL would be the correct answer.