The thin segment of the nephron loop's descending limb

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.

A. prostate gland: The prostate secretes a slightly acidic fluid that contains enzymes and helps activate sperm. While it contributes to the semen, its primary role is not the initial neutralization of the urethra before ejaculation. Its secretions are mixed with sperm during the emission phase of the male sexual act.

B. bulbourethral gland: These glands, also known as Cowper's glands, secrete a clear, alkaline mucus into the spongy urethra during sexual arousal. This fluid neutralizes traces of acidic urine that could be harmful to sperm and provides lubrication for the glans. This occurs prior to the actual ejaculation of semen.

C. epididymis: The epididymis is the site for sperm storage and maturation rather than an accessory secretory gland for urethral neutralization. It adds a small amount of fluid to the sperm bolus, but this fluid does not enter the urethra until the moment of ejaculation. It lacks the volume and pH to neutralize the entire urethral pathway.

D. seminal glands: These glands produce a yellowish, alkaline fluid rich in fructose that makes up about 70 percent of semen. While the fluid is alkaline, it is released during ejaculation to neutralize the acidic environment of the vagina. It does not serve as the primary pre-ejaculatory urethral neutralizer.