This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endometriosis and Infertility, Subject name: Gynaecology & Obstetrics
[{'content': "A male with azoospermia. On examination size of testis normal FSH normal testosterone normal. Most probable cause is: \nSelect and explain. \nA. MAL descended testis, B. Klinefelter's syndrome, C. Kallmann's syndrome, D. VAS obstruction", 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. is d, i.e. VAS obstructionSince all FSH, LH and Testosterone are normal therefore, it has to be an obstructive cause. Amongst the option, VAS obstruction is the only obstructive cause and hence our answer.', 'role': 'assistant'}]