Answer:
The correct answer would be smooth muscle contractions.
The testes ducts include seminiferous tubules, rete testis, epididymis, vasa deferens and urethra.
The seminiferous tubules serves as the site of sperm formation. They then migrate to epididymis for storage and maturation.
The sperm then migrate to vasa deferens from epididymis when the penis gets erected.
When sufficient stimulation is achieved, the vasa deferens propels the sperm forward with the help of smooth muscle contractions.