How have nuclear power plants increased the output of electricity since 1990?

• A. Increasing energy efficiency through cogeneration
• B. Building more wind farms
• C. They have used cogeneration
• D. They have increased imports of energy

Answer: (C)

Cogeneration, or combined heat and power, captures the heat that would normally be wasted in electricity production and uses it for other useful work, like district heating or industrial processes. This makes energy use much more efficient: you get more useful energy output from the same amount of fuel. For nuclear plants, applying cogeneration means more of the energy from the fuel is put to work, so the plant can supply more electricity to the grid or use fuel more effectively to meet higher demand. That direct link between using waste heat to gain additional usable output is why this option best explains changes in nuclear plant electricity output since 1990. The other ideas describe adding external sources or imports, which don’t reflect how the plant’s own efficiency improvements increase its electrical output.