The united states uses which source of energy to produce almost 40 percent of its electricity

Coal is responsible for 40% of the energy produced in the USA.

Explanation:

Coal is responsible for about 40% of all electricity produced in the USA, even though there are several campaigns to decrease the use of fossil fuels such as coal, for energy production, due to the growing climate changes and degradation to nature that provoke. However, coal presents itself as a cheap and easily available source of energy, which explains its widespread use in the country.

it takes hundreds of years to become stable.

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