This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Male Reproductive System, Subject name: Physiology
For male differentiation to occur during embryonic development, testosterone must be secreted from the testes. What stimulates the secretion of testosterone during embryonic development? 
Select and explain. 
A. LH from the maternal pituitary gland, B. HCG, C. Inhibin from the corpus luteum, D. GnRH from the embryo's hypothalamus
B: HCG
Answer: B: HCG 
Explanation: HCG also binds to LH receptors on the interstitial cells of the testes of the male fetus, resulting in the production of testosterone in male fetuses up to the time of bih. This small secretion of testosterone is what causes the fetus to develop male sex organs instead of female sex organ.