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
[{'content': 'Drug used for penile erection - \nSelect and explain. \nA. Sildenaphil, B. Apomorphine, C. Papaverine, D. All of the above', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is'd'i.e., All of the above[Ref KDT fl/e p. 303-304 6 &/e p. 296; Katzung LLth/e p. 197)Drugs used in erectile dysfunctionPhosphodiesterase-S inhibitors (Sildenafil, Todafil, Vardenafil)Alprostadil (Prostaglandin El)", 'role': 'assistant'}]