This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
[{'content': 'Pulmonary hypeension in COPD is due to - \nSelect and explain. \nA. Constriction of pulm vessels, B. Hypoxia, C. Interstitial fibrosis, D. Bronchoconstriction', 'role': 'user'}, {'content': 'Answer: A \nExplanation: pulmonary hypeension in COPD is Category 3. Pulmonary hypeension associated with hypoxemic lung disease Key feature: chronic hypoxia with mild elevation of PAP Includes: * Chronic obstructive lung disease * Interstitial lung disease * Sleep-disordered breathing * Alveolar hypoventilation disorders * Chronic exposure to high altitude * Developmental abnormalities ref:Harrison&;s principles of internal medicine,ed 18,pg no 2078', 'role': 'assistant'}]