Which of the following endoparasites of humans does show viviparity?

Explanation

Trichinella spiralis is a nematode parasite, occurring in rodents, pigs, horse, bears and humans, and is responsible for the disease trichinosis. It is sometimes referred to as the "pork worm" due to it being found commonly in undercooked pork products. Trichinella spiralis is the smallest known nematode parasite of humans. The males measure about 1.4 mm to 1.6 mm in length and the females are twice the size of the males. The body of the worm is more slender at the anterior then at the posterior end. In females the uterus is contained in the posterior portion of the worm and is filled with the developing eggs. The anterior end of the female contains hatching juveniles.