The best answer is (1)
Fossil fuels are commercially available as an energy source.
They are very easy to find. More and more extractions of fossil fuels is going on everyday. With advancement in science and technology, the refineries and extraction procedures have improved a lot. This makes their availability even better.
Fossil fuels are also easily combustible. Most combustion engines need to be powered with little amount of fuel to produce large amount of energy. Very large amounts of electricity can be generated from fossil fuels.
Answer:
An amount that has to be paid or spent to buy or obtain something is called cost.
Mutation can cause instant adaptation while natural selection is the process by which adaptation occurs over a series of generations.
Its renewed again and again by natural water cycle
