Which of the following resources cannot be easily replenished?

Fossil fuels cannot be easily replenished because they form over millions of years from the remains of ancient organic matter. This process occurs under specific geological conditions and requires significant time, making it a non-renewable resource. While fossil fuels can provide a large amount of energy relatively quickly, the rate at which they are extracted and consumed far exceeds the rate at which they are naturally replenished. Consequently, once fossil fuels are depleted, they cannot be replaced within a human timescale, leading to sustainability concerns as reserves dwindle.

In contrast, resources like wind energy and solar energy are considered renewable as they are naturally replenished by ongoing natural processes. Biodiesel, while derived from biological sources, can be regenerated more quickly than fossil fuels, as it is produced from crops that can be replanted and harvested regularly. This distinguishes it further from fossil fuels in terms of replenishment.