- Taenia (IV): A flatworm (phylum Platyhelminthes); it is a tapeworm — parasitic, ribbon-like body.
- Convoluta (VI): Also a flatworm (Platyhelminthes), free-living — found in aquatic habitats.
The other options are:
- Euspongia (I): Porifera (sponges) — not flatworms.
- Aurelia (II): Cnidaria — jellyfish group.
- Beroe (III): Ctenophora — comb jellies.
- Wuchereria (V): Nematoda (roundworm) — causes filariasis.