A 30-Year-Old Man Comes to the Office Due to Infertility

A 30-year-old man comes to the office due to infertility. He has married for 5 years and but failed many times to concive , his partner has 2 child from the previous marriage ,on examination you find the patient has small testes. He has normal male pattern facial and pubic hair. Further laboratory testing reveals a decreased sperm count and normal serum testosterone level. Which of the following is the most likely cause of these findings?

A) Kallmann syndrome
B) 5-alpha reductase deficiency
C) Klinefelter syndrome
D) Androgen use
E) Hyperprolactinemia