Why are fossil fuels a relatively short-term source of energy

Fossil fuels are non-renewable energy resource

Explanation:

Non-renewable resources are those that are not regenerated in nature at rates equivalent to their use. They include oil, coal and other minerals. Our lives and those of future generations are completely dependent on these resources.

the solute can move "downhill," from regions of higher to lower concentration, relying on the specificity of the protein carrier to pass through the membrane. this process is called passive transport or facilitated diffusion, and does not require energy.