This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Parasitology Pa 2 (Helminthology), Subject name: Microbiology
Which of the following is viviparous? 
Select and explain. 
A. Strongyloidis stercoralis, B. Trichinella spiralis, C. Enterobius, D. Ascaris
B: Trichinella spiralis
Answer: B: Trichinella spiralis 
Explanation: 1. Viviparous: Worms that lay Larva directly, without egg formation, e.g. Filarial worms, Trichinella and Dracunculus. 2. Oviparous: Lay eggs which hatch out to larva later in the environment- Ascaris, Hookworm, Trichuris and Enterobius 3. Ovoviviparous: Lay eggs containing larva which immediately hatchout, e.g. Strongyloides.