Final answer:
The correct response to the practice of reducing wasteful or unnecessary energy use is energy conservation, which entails both reducing activities that consume energy and increasing the efficiency of energy conversion in various tasks. Option D is correct.
Step-by-step explanation:
The practice of reducing wasteful or unnecessary energy use is called energy conservation. Energy conservation involves two main strategies: (1) reducing activities that use up energy (for example, turning down thermostats or driving fewer kilometers) and (2) increasing conversion efficiencies when performing tasks (such as using more efficient room heaters or cars with better fuel economy).
Modern civilization's reliance on energy is considerable, but the unsustainable levels of consumption and production necessitate a move towards reducing energy use and shifting to non-fossil fuels. While energy remains constant in an isolated system, most energy transformations result in waste heat—a form of energy that is no longer useful for work, indicating the degradation of energy's potential to do work.
The correct answer to the student's question is D) Energy conservation.