A wind turbine is a source of green power, which is electricity generated from renewable sources that have low or zero greenhouse gas emissions. A wind turbine converts the kinetic energy of the wind into mechanical power, which can then be used to generate electricity. Wind power is a clean, abundant, and sustainable form of energy that does not produce air pollution or contribute to climate change. According to the U.S. Department of Energy, wind power accounted for about 8.4% of the total U.S. electricity generation in 2020. The other options are not sources of green power, as they either rely on fossil fuels or nuclear energy, which have significant environmental and social impacts. Clean coal is a term used to describe technologies that aim to reduce the emissions and waste from burning coal, but it is still a carbon-intensive and polluting source of energy. Nuclear fission is a process that splits atoms to release energy, but it also produces radioactive waste that poses long-term health and safety risks. Natural gas captured by hydraulic fracturing, or fracking, is a process that injects water, chemicals, and sand into underground rock formations to release natural gas, but it also causes water contamination, air pollution, and seismic activity. References: LEED v4 Reference Guide for Building Design and Construction, p. 347 1; [U.S. Department of Energy website]