Helminths are the group of free living and some are parastic organisms present in aquatic, terrestrial environment or in animals or plants respectively. parasitic helminths are the group of worms or organisms that lives inside the GI tract or other parts of the body of host and makes them weak. The two major groups of parasitic helminths are -
Flatworms (platyhelminths) is a parasitic helminths, have leaf like body which is thin and segmented while roundworms or nematode have cylindrical and unsegmented body.
Thus, the correct answer is - flatworms and roundworms.
