This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Hypeension, Subject name: Medicine
Which is the best anti-hypeensive drug in pulmonary hypeension? 
Select and explain. 
A. Bosentan, B. Amlodipine, C. Frusemide, D. Digoxin
A: Bosentan
Answer: A: Bosentan 
Explanation: Endothelin receptor antagonist Bosentan is approved by US FDA and improves exercise tolerance in 6-minute walk test. Amlodipine Not approved by US FDA and only 20% respond to CCB in the long term. Diuretics Will worsen PAH Digoxin Used in CHF and no role in PAH