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: Pharmacology
Which of the following is used to treat severe pulmonary hypertension ? 
Select and explain. 
A. Angiotensin I, B. Omapatrilat, C. Bosentan, D. Endothelin
C: Bosentan
Answer: C: Bosentan 
Explanation: None