Answer:
The correct answer is 3. Coal, natural gas and oil are referred to as fossil fuels because they were formed many years ago from the remains of once living organisms.
Step-by-step explanation:
Fossil fuels are hydrocarbon-containing substances such as coal, oil, natural gas, oil shale and tar sands. These are an energy reserve that has been in the ground for millions of years. Here, organic matter has been subjected to a very high pressure, and has been converted into fossil fuels. They are found in the earth's crust and are extracted as a source of energy by combustion. Alternatively, they could have been used as raw material for, among other things, plastic production. The utilization of fossil fuels has been crucial to industrial development.
The burning of fossil fuels is the major source of carbon dioxide emissions, the most important of the greenhouse gases that cause global warming.