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: Surgery
[{'content': 'Which is the most common cause of male infertility \nSelect and explain. \nA. Smoking, B. Varicocele, C. Epididymitis, D. Idiopathic', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Varicocele is the most common cause of male infertility.', 'role': 'assistant'}]