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 7 year old child presents with non productive cough, mild stridor since 6 months. On oral antibiotics, patient is improving but suddenly develops wheezing, productive cough, mild fever. X-ray shows hyperlucency and PFT shows obstructive curve. Most probable diagnosis is - 
Select and explain. 
A. Post viral syndrome, B. Bronchiolitis obliterans, C. Follicular bronchitis, D. Pulmonary alveolar microlithiasis
B: Bronchiolitis obliterans
Answer: B: Bronchiolitis obliterans 
Explanation: Ans. is 'b' i.e., Bronchiolitis obliterance