The answer would be:
D. Alternative energy sources are often too impractical to use.
Considering our growing population, our resources are slowly being depleted. We should not forget that we only have one world that we can live in, and it would be PRACTICAL if we develop more technology and research on alternative energy sources. Although one may think that the cost of alternative energy is high, the long-term effect will help for the future of sustainability.
Alternative energy sources makes use of renewable resources, like solar, hydro-, wind, geothermal energy. These are resources that do not deplete easily and can be replenished. Water though is non-renewable, however, its use as an alternative energy resource works as a generator of energy and not used as the energy itself.
I hope you had the time to read this, awareness is key! (Hope this helped you!)
