Final answer:
The dartos and cremaster muscles regulate the temperature of the testes by contracting or relaxing, which either brings the testes closer to the body to conserve heat or lowers them away to facilitate heat loss.
Step-by-step explanation:
The dartos and cremaster muscles play a crucial role in the male reproductive system by regulating the temperature of the testes. This is the correct answer to the question. Their function is not related to pushing sperm along the ductus deferens, allowing ejaculation, or causing penile erection.
The dartos muscle is a layer of smooth muscle found in the subcutaneous tissue of the scrotum, which contracts to wrinkle the scrotal skin, reducing its surface area and conserving heat. The cremaster muscle surrounds the testes and contracts to pull the testes closer to the body, helping to keep them warm in cold conditions. In warmer conditions, these muscles relax, allowing the testes to lower away from the body, thereby increasing surface area to facilitate heat loss.