Final answer:
The vas deferens carries sperm out of the testes, transporting them from the epididymis to the urethra where they are mixed with fluids from the prostate gland and seminal vesicles to form semen.
Step-by-step explanation:
The tube that carries sperm out of the testes is the vas deferens. This tube is responsible for transporting sperm from the epididymis to the urethra during ejaculation. Along this pathway, semen is formed when the sperm mix with fluids from the prostate gland and seminal vesicles. These fluids provide nutrients for the sperm and create a suitable pH for sperm viability. It is important to note that while the epididymis is where sperm mature, it is the vas deferens that physically carries the sperm away from the testes and towards the urethra for ejaculation.