Answer:
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. Explanation: The entomologist E. O. Wilson has characterised parasites as "predators that eat prey in units of less than one". Parasites include single-celled protozoans such as the agents of malaria, sleeping sickness, and amoebic dysentery; animals such as hookworms, lice, mosquitoes, and vampire bats; fungi such as honey fungus and the agents of ringworm; and plants such as mistletoe, dodder, and the broomrapes. There are six major parasitic strategies of exploitation of animal hosts, namely parasitic castration, directly transmitted parasitism, trophically transmitted parasitism, vector-transmitted parasitism, parasitoidism, and micropredation.
They have their tentacles which house cells called<span> cnidocytes.</span>
The correct option is C.
Roundworm belongs to the kingdom animalia and to the phylum nematoda. It has round, unsegmented, smooth and thin body which can grow to the maximum of four feet in length. It has a bilateral symmetry. A roundworm has no skeleton and it reproduces sexually.