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: Pediatrics
A 3 month old child has moderate fever and non productive cough and mild dyspnea. After course of mild antibiotic the condition of the child improved transiently but he again developed high fever, productive cough and increased respiratory distress. Chest X ray shows hyperlucency and PFT shows obstructive pattern. Most probable diagnosis is: 
Select and explain. 
A. Alveolar microlithiasis, B. Post viral syndrome, C. Follicular bronchitis, D. Bronchiolitis obliterans
D: Bronchiolitis obliterans
Answer: D: Bronchiolitis obliterans 
Explanation: Bronchiolitis obliterans is a rare chronic obstructive lung disease characterized by complete obliteration of the small airways following a severe insult. The most common form in children is postinfectious, following a lower airway tract infection commonly with adenovirus. Children with bronchiolitis obliterans usually experience dyspnea, coughing, and exercise intolerance. Chest radiograph abnormalities include evidence of heterogeneous air trapping and airway wall thickening. Ref: Federico M.J., Stillwell P., Deterding R.R., Baker C.D., Balasubramaniam V., Zemanick E.T., Sagel S.D., Halbower A., Burg C.J., Kerby G.S. (2012). Chapter 19. Respiratory Tract & Mediastinum. In W.W. Hay, Jr., M.J. Levin, R.R. Deterding, J.J. Ross, J.M. Sondheimer (Eds), CURRENT Diagnosis & Treatment: Pediatrics, 21e.