This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Histamine, 5-HT and PGs, Subject name: Pharmacology
prostacyclin agonist which is usually given oral. 
Select and explain. 
A. Teleprost, B. Iloprost, C. Riociguat, D. Selexipag
D: Selexipag
Answer: D: Selexipag 
Explanation: * Selexipag is the only PGI2 drug which can be given oral route * Prostacyclin analogue like iloprost, treprostinil can be given i/v or s.c or inhaltional route.