Which of the following is a characteristic of renewable energy sources?

Renewable energy sources are characterized by their ability to regenerate naturally over short periods. This means that they can provide a sustainable supply of energy without being depleted as long as they are managed sustainably. Sources such as solar, wind, hydro, and geothermal energy are constantly replenished by natural processes, making them a key component of sustainable energy strategies.

The other options do not accurately represent renewable energy sources. The notion that renewable energy can be exhausted contradicts the fundamental principle of renewability, which is based on the natural cycles that replenish these energy types. Similarly, the requirement of fossil fuels does not apply to renewable sources, as their defining characteristic is to provide energy without relying on fossil fuels. Lastly, renewable energy does not depend on nuclear reactions, which are associated with non-renewable sources of energy and come with their own set of challenges and waste management issues. Thus, the assertion that renewable energy recurs naturally is the defining characteristic that underscores its sustainability and viability as an energy source.