The correct answer is 2. Ejaculatory ducts.

The ejaculatory ducts are responsible for transporting sperm from the testes to the outside through the urethra. They play a crucial role in the male reproductive system, providing a conduit for the passage of sperm during ejaculation. Leydig cells are involved in testosterone production, vasa efferentia are part of the testicular anatomy, and the rete testis is a network of tubules within the testis, but the ejaculatory ducts specifically transport sperm to the urethra.