Coal, oil and natural gas are fossil fuels. They have been in existence for a very very long time. Many people use these fuels as a type of energy. However, fossil fuels are non-renewable; if these are used up completely they will never be available again. It is therefore important to conserve fossil fuels. We can do so by using alternative ways of energy.
Just a question why is everyone asking about conservation of fuel. This is the third time I'm answering this question