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: ENT
A 3 year old child with cystic fibrosis presents with weight loss, irritability, and a chronic productive cough. On physical exam, he is febrile and lung exam reveals intercostal retractions, wheezing, rhonchi, and rales. Chest x-ray demonstrates patchy infiltrates and atelectasis and Gram's stain of the sputum reveals slightly curved, motile gram-negative rods that grow aerobically. The microorganism responsible for this child's pneumonia is also the most common cause of which of the following diseases? 
Select and explain. 
A. Croup, B. Epiglottitis, C. Meningitis, D. Otitis externa
D: Otitis externa
Answer: D: Otitis externa 
Explanation: None