Question

built in the 1970s, raccoon mountain is a pumped - storage hydropower facility (a “water - battery”) located in the united states along the tennessee river. when energy demand is low, excess power from the regional electric utility’s nuclear plants is used to pump water (from a lower reservoir filled from the tennessee river) up a shaft to the summit lake, where the water is stored as gravitational potential energy. when energy demand peaks, the water drains down from the summit lake, spinning turbines and generating upward of 1,700 megawatts of power—enough to power one million homes for twenty hours. which choice best states the main purpose of the text? a) to discuss the benefits of a new energy technology. b) to encourage regional electric utilities to build energy storage facilities. c) to point out the differences between two methods of energy generation. d) to explain the basics of how a specific energy technology works.

Explanation:

The text details how the Raccoon Mountain pumped - storage hydropower facility operates during low and high energy demand periods, explaining the basic working mechanism of this specific energy technology. It doesn't focus on benefits of new energy technology (it's not new as it's from the 1970s), doesn't encourage building of facilities, and doesn't compare two energy - generation methods.

Answer:

D. To explain the basics of how a specific energy technology works.