Most animals that live in deep oceanic water are?
Detritivores
The correct option is option A.
Explanation for the correct option:
Detritivores: Detritivores are organisms that depend on decaying organisms. These decompose the organic material and are included in the last trophic level of an ecosystem. In deep oceanic water, there is no light at all, high pressure, and a lack of oxygen. There are decaying skeletons of protozoans and decaying organic matter for food. So, only those animals that can live in this condition and feed on these are found here like crustaceans, brittle starts, sea lilies, sea cucumber and some fishes like chimera and angular fish.
Explanation for the incorrect option:
Option B: Tertiary consumers like killer whales are not found in the deep ocean but in the upper region.
Option C: Secondary consumers like small fishes are not found in the deep ocean.
Option D: Primary consumers like zooplankton are found at the twilight zone.
Final answer: Most animals that live in deep oceanic water are detritivores.