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
Pulmonary hypeension in COPD is due to - 
Select and explain. 
A. Constriction of pulm vessels, B. Hypoxia, C. Interstitial fibrosis, D. Bronchoconstriction
A: Constriction of pulm vessels
Answer: A: Constriction of pulm vessels 
Explanation: 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