Hello!
The answer is: D. Coal
Why?
Coal power plants burn coal in to get steam, the steam flows into a turbine which is coupled to an electrical generator.
Coal power plants work burning high amounts of coal into a boiler, generation a lot of steam under extreme pressures. The steam is obtained when the water is heated by the burning coal, then the steam is cooled, being transformed in liquid water again (due the condensation process) and it's sent back on a cyclical process.
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