Answer:
Option 4, Organisms in level D are heterotrophic.
Explanation:
Generally in a energy level or trophic level system, organisms are arranged on a pyramid scale in such a way that organism lying at the level A or the base of the pyramid are producers. They obtain energy from the sun and produce food for other organisms. Organism in level B is a herbivore which feed upon the plants to gain food and energy. In level C organisms that feed upon herbivores i.e the carnivores lies. At level D lies the microorganisms that feed upon dead remains of high order animals and plants. Hence, organisms at level D are called heterotrophs.
Thus, option 4 is correct