After food, fossil fuel is humanity's most important source of energy. There are three major fuels -- coal, oil and natural gas. Coal is used primarily to produce electricity. It therefore provides us with light, motive power from electric motors, and our many electronic devices. Oil gives us our mobility, our cars, planes, trains, trucks and boats. Natural gas is used primarily to produce heat, for our buildings, hot water, and industrial processes.
1.This sentence means that this is very important for people , and this is source of energy.
2.Fossil fuels, also known as mineral fuels, are hydrocarbon-containing natural resources such as coal, petroleum and natural gas. The utilization of fossil fuels has fueled industrial development and largely supplanted water driven mills, as well as the burning of wood or peat for heat.
3.http://www.bydesign.com/fossilfuels/lin ... _fuel.html
There are two theories on the origin of fossil fuels: the mainstream biogenic theory and the abiogenic theory. The two theories have been intensely debated since the 1860s, shortly after the discovery of widespread petroleum. According to the biogenic theory, fossil fuels are the altered remnants of ancient plant and animal life deposited in sedimentary rocks.
1.This sentence is taking about two theories on the origin of fossil fuels.