Answer:
Coal
Step-by-step explanation:
The United States has the largest coal reserves in the world, with an estimated 250 billion tons of recoverable coal. Coal has been a significant source of energy in the United States for many years, and the country has a long history of coal mining and production. Coal is an abundant and relatively cheap fossil fuel, which has made it an attractive energy source for many industries, including power generation, steel production, and cement manufacturing. While the use of coal has declined in recent years due to concerns over its environmental impact and the rise of alternative energy sources, coal is still an important part of the energy mix in the United States and around the world