This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System, Subject name: Medicine
A 50-year-old man working in a coal mining factory for 16 years develops symptoms of progressively worsening breathlessness and cough with expectoration. A spirometry was performed and his values were: FEV1 - 1.4 L/min, FVC 2.8L/min . What could be the cause? 
Select and explain. 
A. Silicosis, B. Hypersensitivity pneumonitis, C. COPD, D. Idiopathic pulmonary fibrosis
C: COPD
Answer: C: COPD 
Explanation: The FEV1/FVC ratio of the patient is low which indicates obstructive airway disease. Coal workers pneumoconiosis is associated with effects of coal dust on alveolar macrophages leading to the development of chronic bronchitis and COPD. Spirometry Obstructive lung disease Restrictive lung disease FEV1 VC FEV1/FVC RV FRC Low ++ Low+ Low High High Low + Low++ Normal / High Low Low