A 71/2 months old child with cough ,mild stridor is started on oral antibiotics.The child showed initial improvement but later developed wheeze,productive cough,and mild fever.X-ray shows hyperlucency and PFT shows an obstructive curve.The most probable diagnosis is,

• A. Pulmonary alveolar microlithiasis
• B. Follicular bronchitis
• C. Bronchiolitis obliterans
• D. Post viral syndrome