Fossil fuels, including coal, oil, and natural gas, supply 90% of the world's energy. They are hydrocarbons formed from prehistoric plants and animals. The formation process involves photosynthesis, decomposition, and compression over millions of years. Oil and gas originate from marine organisms, while coal comes from land vegetation. These fuels are extracted from deep underground. However, fossil fuels are finite and unsustainable as they cannot be replenished within human time scales.

What percentage of the world's energy is supplied by coal, oil, and natural gas?

• 90%

• 70%

• 100%

• 50%

Which process allows plants to convert the sun's energy into usable energy?

• Decomposition

• Combustion

• Photosynthesis

• Respiration

What happens to prehistoric organic matter over time to form fossil fuels?

• It is consumed by animals

• It dissolves in water

• It is compressed by pressure and heat

• It evaporates

From what type of organisms are oil and gas primarily formed?

• Dinosaurs

• Marine organisms

• Insects

• Land plants

Why are fossil fuels considered unsustainable?

• They are too expensive to extract

• They are renewable

• They cannot be replaced within human time scales

• They are abundant