Final answer:
A vasectomy is a true form of male sterilization where the vas deferens is cut or sealed, preventing sperm from being ejaculated. After the procedure, the sperm stay in the epididymis, and while semen is still ejaculated, it no longer contains sperm, rendering fertilization impossible.
Step-by-step explanation:
The statement in the question, "Vasectomy involves cutting and sealing the ductus deferens," is true. A vasectomy is a surgical sterilization procedure for men in which the vas deferens is blocked so that sperm cannot be ejaculated. During this procedure, a small section of the ductus (vas) deferens is removed or sealed, interrupting the path taken by sperm. If sperm do not exit through the vas deferens, either because a man has had a vasectomy or because he has not ejaculated, the sperm will remain in the region of the testis called the epididymis. The epididymis is where sperm mature and are stored before ejaculation.
When a man has a vasectomy, semen is still ejaculated, but it will be devoid of sperm because the passage of sperm from the testes to the urethra has been obstructed. As such, fertilization of an egg is not possible without the presence of sperm. It's important to note that the testes continue to produce sperm after a vasectomy, but these sperm are reabsorbed by the body.