This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
In cystic fibrosis the most frequent pulmonary pathogen is 
Select and explain. 
A. Klebsiella, B. Enterococci, C. Staphylococci, D. Pseudomonas
D: Pseudomonas
Answer: D: Pseudomonas 
Explanation: Pseudomonas aeruginosa species, in particular, colonize the lower respiratory tract, first intermittently and then chronically.