The correct option is B Oyster, ship worm, octopus, cuttle fish
Liver flukes and tapeworm are Platyhelminthes while roundworm and guinea worm are nematodes.
Prawn, millipede and crab are arthropods, while Nereis is an annelid.
Sea urchin and sea lily are echinoderms, while sea fan and sea pen are Cnidarians.
Oyster, ship worm, octopus, cuttle fish all belong to the phylum Mollusca.
Thus, the correct answer is option B.