Fertilization generally occurs in the

A. not develop secondary sex characteristics: Secondary sex characteristics, such as muscle growth and hair distribution, are driven by testosterone produced by interstitial cells. Since LH levels are normal, these cells will still be stimulated to produce adequate testosterone. The boy would likely appear physically mature in terms of external male characteristics.

B. have impaired function of interstitial cells: Interstitial endocrine cells are specifically regulated by luteinizing hormone, which the question states is functioning normally. These cells will continue to synthesize testosterone regardless of the FSH deficiency. Their endocrine function remains intact because their primary tropic hormone is still present in the circulation.

C. be impotent (unable to have an erection): Erection is a neurovascular reflex mediated by the parasympathetic nervous system and is not directly dependent on FSH. While low testosterone can decrease libido, LH is present to maintain testosterone levels. Therefore, the physiological mechanism for erection should remain functional in this mature male.

D. be unable to produce viable sperm: Follicle-stimulating hormone is strictly required to stimulate the sustentacular cells to facilitate the final stages of sperm maturation. Without FSH, the process of spermatogenesis cannot be completed effectively, leading to infertility. The individual would produce few or no functional spermatozoa despite normal hormonal levels.

B. false: Sexual reproduction entails the union of two gametes, specifically a haploid sperm and a haploid secondary oocyte, to form a diploid zygote. The gonads are the sites of gametogenesis but do not merge during fertilization. The fusion of genetic material occurs at the cellular level through a process called syngamy.