Which of the following endoparasites of humans does show viviparity?
1. Enterobius vermicularis
2. Trichinella spiralis
3. Ascaris lumbricoides
4. Ancylostoma duodenale

In nematodes:
1. The head is radially symmetrical while the body is bilaterally symmetrical.
2. The body is radially symmetrical while the head is bilaterally symmetrical.
3. Both body and head are radially symmetrical.
4. Both body and head are bilaterally symmetrical.