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': 'Alpha 1a adrenergic blocker giving symptomatic relief in BPH is: \nSelect and explain. \nA. Tamsulosin, B. Prazosin, C. Doxazosin, D. Tolazoline', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]