**Core Concept**
The patient's presentation suggests an evolving respiratory condition with a shift from a non-productive cough to a productive cough, wheeze, and hyperlucency on chest X-ray (CXR). This pattern, combined with obstructive pulmonary function test (PFT) results, points towards an exacerbation of a chronic condition.

**Why the Correct Answer is Right**
The patient's symptoms and CXR findings are indicative of an allergic bronchopulmonary aspergillosis (ABPA) exacerbation in the context of pre-existing asthma. ABPA is a hypersensitivity reaction to Aspergillus species, often seen in patients with asthma or cystic fibrosis. The presence of hyperlucency on CXR and obstructive PFT curve supports the diagnosis. Hyperlucency is a characteristic finding in bronchiectasis, which is a common complication of ABPA.

**Why Each Wrong Option is Incorrect**

**Option A:** This option would be incorrect as it does not account for the patient's chronic symptoms and the presence of hyperlucency on CXR. Cystic fibrosis (CF) is a possibility, but the lack of specific CF symptoms (e.g., meconium ileus, pancreatic insufficiency) and the presence of mild stridor make it less likely.

**Option B:** This option is incorrect as it does not explain the patient's chronic symptoms and the presence of hyperlucency on CXR. Eosinophilic pneumonia is a possibility, but it is typically associated with a different radiographic pattern and a more pronounced eosinophilia.

**Option C:** This option is incorrect as it does not account for the patient's chronic symptoms and the presence of hyperlucency on CXR. Bronchiolitis obliterans syndrome (BOS) is a complication of lung transplantation, which is not relevant to this patient's presentation.

**Option D:** This option is incorrect as it does not explain the patient's chronic symptoms and the presence of hyperlucency on CXR. Croup is a viral infection characterized by a barking cough and stridor, but it does not typically result in hyperlucency on CXR or an obstructive PFT curve.

**Clinical Pearl / High-Yield Fact**
ABPA is a complication of asthma that can lead to bronchiectasis and other pulmonary complications if left untreated. It is essential to recognize the characteristic symptoms and radiographic findings of ABPA to initiate prompt treatment.

**Correct Answer:** C. Allergic bronchopulmonary aspergillosis (ABPA).