The answer is renewable resources because they can be renewed in a reasonable period through natural processes.

Renewable resources are those resources that either never run out or are replenished within a reasonable period of time through natural processes. These resources are crucial for sustaining life on Earth and are often considered more environmentally friendly compared to non-renewable resources.

There are several reasons why renewable resources are called as such:

1. Never run out:
- Renewable resources, such as solar energy and wind energy, are derived from sources that are virtually inexhaustible. The sun will continue to emit light and heat for billions of years, and wind will always be present on Earth.
- These resources have the potential to provide energy indefinitely without depleting their source.

2. Replenished through natural processes:
- Some resources, like forests and crops, are renewable because they can be regrown or replaced within a reasonable period of time.
- Trees can be replanted after being harvested, and crops can be grown again in the following season.
- This replenishment occurs through natural processes like photosynthesis and seed dispersal.

3. Environmentally friendly:
- Renewable resources generally have a lower environmental impact compared to non-renewable resources.
- For example, the use of solar or wind energy for electricity generation produces minimal greenhouse gas emissions and reduces dependence on fossil fuels, which contribute to climate change.
- Additionally, renewable resources often have lower pollution and waste outputs.

4. Sustainability:
- The use of renewable resources promotes sustainability by ensuring that future generations will have access to the same resources and environmental services.
- By relying on renewable energy sources, we can reduce our dependency on finite resources like coal, oil, and natural gas.

In conclusion, renewable resources are called as such because they either never run out or are replenished within a reasonable period of time through natural processes. These resources play a vital role in sustaining life on Earth while minimizing environmental impact and promoting sustainability.