Renewable energy sources are characterized by their ability to be naturally replenished over time. This means that resources such as solar, wind, hydro, and geothermal energy are continuously available as they rely on natural processes that occur in the environment. For example, solar energy is generated by the sun's radiation, which is abundant and will be available for billions of years, while wind and hydro power harness natural atmospheric and water flow processes that are naturally occurring and do not diminish with use.
In contrast, options that suggest that renewable energy sources are exhaustible or produce high levels of greenhouse gases do not align with the fundamental principles of what makes a source renewable. Furthermore, while the cost of renewable energy technologies has historically been higher compared to fossil fuels, the rapid advancements in technology and economies of scale have led to decreasing costs in many cases, making them increasingly competitive. Thus, the statement that they are naturally replenished over time adequately captures the essence and primary benefit of renewable energy sources.