The correct response is:
The Sun continually replenishes the Earth's energy, but the Earth has a constant amount of matter.
Explanation: In food webs and energy pyramids, energy flows in one direction—from the sun to producers and then through various consumers—illustrating the transfer of energy through an ecosystem. Energy is not recycled; it dissipates as heat, so it is continually replenished by the sun. In contrast, matter (such as nutrients) cycles within ecosystems; it is reused and recycled among different organisms and compartments of the ecosystem. Thus, while energy flow is unidirectional and requires continual input from the sun, matter is part of a closed loop system that can be cycled through various forms and organisms.