A Roundworm or Nematode has a "tube" like body within a tube, with a fluid- filled cavity in between the tubes.
Most nematodes are parasites, such as ascarids, filarids, pinworms, hookworms, and...
the_________ body plan is chacterized by bilateral symmetry, a flatten body cephalization a digestive system with a pharynx for feeding .
a. flatworm
b.annelid
c. cechinoderm
d. roundworm