This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
All are causes of pulmonary hypertension except- 
Select and explain. 
A. Hyperventilation, B. Morbid obesity, C. High altitude, D. Fenfluramine
A: Hyperventilation
Answer: A: Hyperventilation 
Explanation: None