To solve this problem, we need to identify which of the given endoparasites of humans exhibits viviparity. Let's analyze each option:$\newline \bullet$Option 1: Ancylostoma duodenale$\newline$ - Ancylostoma duodenale is a type of hookworm.$\newline$ - It is an oviparous parasite, meaning it lays eggs.$\newline$ - Therefore, it does not exhibit viviparity.$\newline \bullet$Option 2: Enterobius vermicularis$\newline$ - Enterobius vermicularis, also known as the pinworm, is an oviparous parasite.$\newline$ - It lays eggs around the host's anus.$\newline$ - Therefore, it does not exhibit viviparity.$\newline \bullet$Option 3: Trichinella spiralis$\newline$ - Trichinella spiralis is a nematode that causes trichinosis.$\newline$ - It is known for being viviparous, as it gives birth to live larvae.$\newline$ - Therefore, it exhibits viviparity.$\newline \bullet$Option 4: Ascaris lumbricoides$\newline$ - Ascaris lumbricoides is a large intestinal roundworm.$\newline$ - It is oviparous, laying eggs that are passed in the host's feces.$\newline$ - Therefore, it does not exhibit viviparity.$\newline$Based on the analysis, the correct answer is Option 3: Trichinella spiralis, as it is the only endoparasite among the options that exhibits viviparity.