Fred went to the doctor because his body was not producing semen. which part of fred's body was most likely functioning incorrectly to cause this problem.

The answer would be testes.

Semen or seminal fluid refers to the organic fluid which contains spermatozoa.

The semen is produced by testes and associated reproductive glands such as seminal vesicles, prostate glands, and bulbourethral gland.

The testes and other glands are located mainly in the scrotum of the person.

Thus, the testes and other reproductive glands may not function properly if Fred is not producing semen.

the answer is "a.) well–developed vascular system."

explanation:

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%