Fossil fuels—such as coal, oil, and natural gas—come from ancient, and long dead, plant and animal matter. These fuels have been generated through millions of years of the Earth's geologic processes. Most fossil fuel reserves are found underground, relatively close to the Earth's surface. At the current rate that human civilization is burning fossil fuels for energy, the Earth's geologic processes have no chance of keeping pace. This means that fossil fuels are a energy resource.
A.
synthetic
B.
nonrenewable
C.
plentiful
D.
renewable