Currently available natural gas reserves are expected to last another 75 years at the current rate of consumption.

The least efficient and most abundant form of coal is lignite; after this comes bituminous coal, then, lastly, anthracite. Anthracite is a very hard form of coal with an extremely high carbon content. Anthracite also burns the cleanest of any coal, but unfortunately it is the least abundant and hardest to reach form of coal. Charcoal is not coal at all, but rather compressed and burned wood, consisting mainly of carbon and any remaining ash.

Clean coal technology is a promising solution to minimizing pollution from coal plants, and coal is one of the most abundant fossil fuels on the planet, with reserves potentially lasting up to three hundred years. Coal is also very energy-dense when compared to biomass or other renewable energy sources; however, the sulphur content of coal varies based on geographic location, and in areas that depend on locally sourced, sulphur-rich coal, the resulting emissions contribute heavily to acidic precipitation.

The United States is 5% of the world Population and consumes 25% of global fossil fuel production. In addition, North America peaked in oil production in the 1970's which, when combined with a disproportionately high demand, results in a national dependence on foreign-sourced oil.

Fracking is the process of blasting rocks with a mixture of water, sand, and chemicals in order to extract oil from a well. It has grown in popularity in recent years, particularly in the U.S. and Canada.

Fossil fuels are notoriously dirty sources of energy, and their pollution is often expensive and/or difficult to control.

U-235 differs from U-238 in that U-235 is able to produce a fission chain reaction. U-238 is the most common isotope of uranium, with the U-235 isotope constituting less than 1% of natural sources. Uranium enrichment is the process by which U-235 is separated out, and it is this product that is most commonly used to manufacture nuclear weapons. Pu-239 is produced from U-238 and can be used for nuclear weapons as well, but Pu-239 is not an answer choice.

Producing nuclear energy is a lot cleaner than most people realize, and while it is expensive (but still profitable), it represents a legitimate option for producing cleaner energy. The main drawback is that the resulting "spent fuel" has to be secured and stored, because it cannot be safely disposed of without significant repercussions.

Dams can be huge boons to local economies, and are a landmark of human engineering and achievement; however, they do carry serious consequences to the natural environment. They lead to sediment buildup, which hurts the flow of nutrients downstream, ruins the natural riverscape, and can cause the area behind the dam to become more shallow.

Dams carry numerous drawbacks, but one benefit of dams that they do not increase air pollution. Hydroelectric power is considered to be one of the cleanest forms of energy.