The correct option is C Sea anemone
Leech (phylum Annelida) is blood-sucking ectoparasites, while tapeworm (phylum Platyhelminthes) is an endoparasite. Plasmodium is a unicellular protozoan which is a parasite of humans but Sea anemone is not known to be parasitic (neither ectoparasite nor endoparasite) Therefore, the correct answer is option C.