**Core Concept**
The question describes a patient with obstructive lung disease, characterized by a reduced Forced Expiratory Volume in one second (FEV1) and a normal Forced Vital Capacity (FVC), with an FEV1/FVC ratio less than 0.7. This indicates airway obstruction. The reversibility with bronchodilators suggests a diagnosis of asthma or chronic obstructive pulmonary disease (COPD) with an asthmatic component.

**Why the Correct Answer is Right**
The reduced FEV1 and normal FVC indicate that the patient has difficulty exhaling air from the lungs within one second, which is a hallmark of obstructive lung disease. The FEV1/FVC ratio less than 0.7 confirms the presence of airway obstruction. The reversibility with bronchodilators suggests that the airway obstruction is due to bronchospasm, which is a characteristic feature of asthma. In asthma, bronchodilators can relax the smooth muscles of the airways, leading to improved lung function.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a reversible component, which is a key feature of the correct diagnosis.
**Option B:** This option is incorrect because it refers to a restrictive lung disease, which is characterized by a reduced FVC and a normal FEV1/FVC ratio.
**Option C:** This option is incorrect because it does not mention bronchodilator reversibility, which is a crucial aspect of the correct diagnosis.

**Clinical Pearl / High-Yield Fact**
The FEV1/FVC ratio is a sensitive indicator of airway obstruction, and a ratio less than 0.7 is a diagnostic criterion for obstructive lung disease. The reversibility with bronchodilators is a key feature that distinguishes asthma from other obstructive lung diseases.

**Correct Answer:** A. Asthma