**Core Concept**
Obstructive lung disease is characterized by airflow limitation due to airway narrowing or obstruction, leading to reduced expiratory flow. Key features include a decreased FEV1/FVC ratio and increased total lung capacity (TLC), reflecting air trapping and hyperinflation.

**Why the Correct Answer is Right**
In obstructive lung diseases like COPD, airflow obstruction results in a FEV1/FVC ratio < 0.70. This ratio is a hallmark diagnostic criterion. Additionally, air trapping causes hyperinflation, leading to increased TLC. This is due to impaired expiration and elastic recoil, which results in lungs retaining more air than normal.

**Why Each Wrong Option is Incorrect**
Option A: The mMRC dyspnea scale grade 2 describes breathlessness with slight exertion, not just when hurrying up inclines. The description is inaccurate and overly specific.
Option C: PEFR may be normal in early or mild obstruction, but decreased lung volume is not a feature of obstructive disease; instead, lung volumes are increased, not decreased.
Option D: Roflumilast is used in chronic bronchitis with exacerbations (Group C in COPD classification), but it is not introduced as a new treatment in Group C—its use is limited and not a primary management strategy.

**Clinical Pearl / High-Yield Fact**
In obstructive lung disease, FEV1/FVC < 0.70 and increased TLC are diagnostic hallmarks. Always check the ratio first—this is the most reliable screening tool for obstruction.

✓ Correct Answer: B. Decreased FEV1/FVC ,TLC is increased