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': "A male with azoospermia found to have normal FSH & testosteron levels & normal size testes. Probable cause is \nSelect and explain. \nA. Vas obstruction, B. Kaltman syndrome, C. Undescended testis, D. Klinefeltor's syndrome", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]