In an ecosystem, there is flow of energy at different trophic levels. This is as follows :

• A

  Primary consumers — Tertiary consumers — Secondary consumers — Decomposers — Producers

• B

  Producers — Primary consumers — Secondary consumers — Tertiary consumers — Decomposers

• C

  Producers — Decomposers — Primary consumers — Tertiary consumers — Secondary consumers

• D

  Producers — Primary consumers — Tertiary consumers — Secondary consumers — Decomposers