The correct answer is: D. Testes.
The testes are the male reproductive organs that produce sperm and testosterone. They are located in the scrotum, which is a sac of skin that hangs below the penis. The testes are made up of many tiny tubes called seminiferous tubules. These tubules are where sperm are produced. Sperm are produced by a process called spermatogenesis. Spermatogenesis begins with the production of spermatogonia, which are immature sperm cells. Spermatogonia divide and differentiate into primary spermatocytes. Primary spermatocytes then divide into secondary spermatocytes. Secondary spermatocytes divide into spermatids. Spermatids are then transformed into mature sperm cells.
The testes also produce testosterone, which is a hormone that is responsible for male sexual development and function. Testosterone is produced by the Leydig cells, which are located in the interstitial tissue of the testes. Testosterone is responsible for the development of secondary sexual characteristics, such as facial hair, a deep voice, and muscle mass. It is also responsible for sexual desire and function.
The testes are an important part of the male reproductive system. They produce sperm and testosterone, which are essential for reproduction.