Roundworms are smooth, thin, tube-shaped worms that are at both ends. Roundworms are the common worms on the earth. Some roundworms reproduce inside their host’s .

open, most common, intestines

Explanation:

They have an open digestive system with a mouth opening that connects straight to their anus. They are the most common animal on the planet and include earthworms. A lot are parasitic and reproduce and live in a hosts intestines. their eggs and sometimes the worm themselves can be passed through feces. Then another animal may eat it or someone steps in it and they become infected

good question .