Benthic organisms are identified as species that live in relation to the bottom (substrate), either to attach to it or to drill, dig and/or walk on a surface. The substrate can be consolidated (rocks, wood, wharf, etc.) or unconsolidated (sand, mud, etc.). Benthic organisms are composed of macroalgae, microalgae and aquatic plants (phytobenthos); animals and many protists (zoobenthos).
So, Tuna isn't a benthic organism and the right answer is Letter D.
Benthic organisms are those that dwell on the bottom of the sea or on the ocean floor. These include sponges, lobsters, crabs, clams, worms, etc. From the given choices, only the tuna will not qualify being benthic. Thus, the answer is letter D.
