This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: A.N.S., Subject name: Pharmacology
[{'content': 'Which of the following is selective alpha antagonist? \nSelect and explain. \nA. Propanolol, B. Prazosin, C. Phentolamine, D. Clonidine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. PrazosinPrazosin is selective alpha 1 blocker which used in patients suffering from BHP. They also used in hypertension. Phentolamine is nonselective alpha blocker. Clonidine is alpha 2 agonists.', 'role': 'assistant'}]