Which of the following describes a non-renewable resource?

A non-renewable resource is specifically defined as a resource that cannot be replenished or regenerated naturally within a human timescale once it has been consumed. This includes resources such as fossil fuels (coal, oil, and natural gas) and certain minerals, which are formed over millions of years through geological processes. Once these resources are extracted and used, they are effectively gone for all practical purposes. This characteristic highlights the finite nature of non-renewable resources, leading to concerns about sustainability and the impact of their depletion on future generations.

In contrast, renewable resources are those that can be naturally replenished, and their availability can be maintained over time, which does not apply to non-renewable resources. A resource available in unlimited quantities does not fit the definition of a non-renewable resource, as non-renewables have a definite limit to their availability. Similarly, resources that are always renewable do not align with the definition of non-renewable resources, as non-renewables are precisely those that cannot be regenerated. Therefore, the description that best fits the nature of non-renewable resources is that they cannot be replaced once consumed.