The correct response is:
The Sun continually replenishes the Earth's energy, but the Earth has a constant amount of matter.
This statement accurately explains why food webs illustrate the flow of energy (as energy is transferred from one organism to another in a linear pathway), while energy pyramids depict how energy diminishes at each trophic level. In contrast, matter cycles through ecosystems (like carbon, nitrogen, and water), remaining constant over time as it is recycled among different forms and organisms.