Answer:
Option B
Step-by-step explanation:
In any food cycle or ecosystem, the top most organisms are the decomposers. They are kept above the tertiary species because when the tertiary species die, these decomposers or micro-organisms feed on them and convert organic material with in them into reusable form/nutrients/chemicals.
These nutrients get mixed with the soil and are reused by the plants and trees (producers) for making food for all other organism in the food chain by entrapping solar energy.
Hence, option B is correct