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
[{'content': 'Which is the best anti-hypeensive drug in pulmonary hypeension? \nSelect and explain. \nA. Bosentan, B. Amlodipine, C. Frusemide, D. Digoxin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 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', 'role': 'assistant'}]