Growth of chest hair, deepening of the voice, and muscle growth are secondary sex characteristics. Which structure or structures produce substances most likely to affect the development of these traits?

The testes produce testosterone, a hormone that promotes male secondary sex characteristics such as chest hair, a deeper voice, and increased muscle growth. The prostate gland contributes fluid to semen, while the ovaries and vulva are not the source of the hormones most associated with these traits. Therefore, the correct choice is testes.

AI-written and checked against the verified answer.