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
A male with azoospermia found to have normal FSH & testosteron levels & normal size testes. Probable cause is 
Select and explain. 
A. Vas obstruction, B. Kaltman syndrome, C. Undescended testis, D. Klinefeltor's syndrome
A: Vas obstruction
Answer: A: Vas obstruction 
Explanation: None