Sustainable energy is defined as

• A. a source of energy that has no effect or impact on currents or future resources
• B. a source of energy that has no long-term impact on ecosystems or resources
• C. energy that never causes emissions
• D. energy that is always available

Answer: (A)

Sustainable energy means using energy in a way that preserves future options and minimizes harm to the environment. The best choice captures that idea by describing a energy source as having no effect or impact on currents or future resources, aligning with the goal of not depleting resources or disrupting natural systems for future generations. In reality, no energy source is truly impact-free, but sustainable energy aims to minimize long-term harm and maintain resource availability. The other statements are too absolute or inaccurate: some imply zero emissions across the entire lifecycle, always-available energy, or no long-term effects, which don’t hold true in practice. This option best reflects the intended purpose of sustainable energy in the given context.