Answer: D
Explanation: A healthy ecosystem is capable of exisitng based on the matter within that ecosystem. Energy is often supplied externally (e.g., the sun, geothermal, etc.) and is stored by the ecosystem in the form of chemical bonds made between the elements. Plants utilize matter (minerals, carbon dioxide, water) within the ecosystem (plus whatever is delivered via asteroid or candy wrappers). Animals depend on the plants for both energy and matter that is transformed into the compunds needed for their existence. Decomposers act to reduce complex matter (plants and animals) back into more basic compounds that then reenter the ecosystem as raw material for he next set of plants, animals, humans, and aliens.