All living members of the class Cyclostomata are:

Correct Answer: (4) Ectoparasite

Explanation:

The class Cyclostomata includes jawless vertebrates such as lampreys and hagfishes. These animals possess a circular, sucker-like mouth adapted for attaching to host fishes.

Lampreys are classic ectoparasites, feeding on the blood and tissues of other fish by attaching to their bodies externally. Though hagfishes are mostly scavengers, they may also show parasitic tendencies. Therefore, all living members of Cyclostomata exhibit ectoparasitic behavior.

Other options are incorrect because:

• Free living – They depend on hosts for nutrition.
• Endoparasite – They live externally, not inside the host.
• Symbiotic – The relationship is harmful to the host, not mutually beneficial.