This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anti-Hypertensive, Subject name: Pharmacology
Which drug is used for treatment of pulmonary hypertension - 
Select and explain. 
A. Calcium channel blockers, B. Todafil, C. Bosentan, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Ans. is 'd' i.e., All of the aboveo Drugs used to treat pulmonary hypertension are act by -1) Direct vasodilators# Calcium channel blockers are the first line therapy if patient responds to vasodilators.2) Increasing effect of NO/cGMP# Phosphodiesterase-5 inhibitors prevent degradation of cGMP and cause vasodilatation.# Drugs are sildenafil and todafil.3) By increasing effect of prostacycline (PGI2)# PGI2 causes pulmonary vasodilatation.# So prostacyclins like epoprostenol, treprostinal, iloprost or beraprost can be used in pulmonary hypertension.4) Decreasing effect of endothelin# Endothelin causes pulmonary vasoconstriction.# Endothelin receptor blockers (endothelin antagonists) are used in pulmonary hypertension.# These are Bosentan and ambrisentan.