One advantage of using ______ fuels is that they are relatively inexpensive.

• A. Fossil
• B. Nuclear
• C. Solar
• D. Wind

Answer: (A)

The main idea is that energy sources differ in how much they cost to produce and deliver. Fossil fuels are relatively inexpensive because there’s a long-established, efficient system for extracting, processing, transporting, and burning them. The infrastructure spans mines, pipelines, refineries, and power plants, and the fuel is abundant in many regions, which helps keep prices down and energy available at a lower per-unit cost. That combination—proven technology, big-scale operations, and readily available fuel—keeps the ongoing cost of generating electricity with fossil fuels comparatively low.

In contrast, other options tend to have higher upfront or capital costs: solar and wind require expensive equipment and installations, and their output can be variable without storage or backup. Nuclear can provide very large amounts of energy, but the plants require substantial investment and long construction times. Those factors often push their overall cost per unit of electricity higher than fossil fuels in the short to medium term, even though they might have lower fuel costs or other benefits in the long run.