Which of the following endoparasites of humans does show viviparity?

Explanation

Trichinella spiralis is a minute nematode parasite that shows viviparity i.e., produces live youngs (larvae) not eggs. The adults of T. spiralis live in the human small intestine, where the females release large numbers of larvae. These larvae bore through the intestine and can cause trichinosis or trichiniasis which has symptoms like diarrohea, nausea, vertigo, pain in limbs and fever etc. Humans get infected after eating imperfectly cooked meat infected with the parasite's larval cysts.