Fossil fuels are made by the decay of living things. because living things are always dying and decaying, why are fossil fuels not a renewable source of energy?
a. they can only be formed by decay of reptiles.
b. they can only be formed by decay of swamp plants.
c. they take millions of years to form.
d. they can only be formed deep under the sea.

The answer is: C. They take millions of years to form.

Fossil fuel is a fuel formed by anaerobic decomposition of buried dead organisms.

If there was oxygen the organic matter would not decomposed and formed oil and gas, because there would be reaction of oxidation.

The age of the organisms and their resulting fossil fuels is typically millions of years

Fossil fuel is mixture (solution) consist of several different hydrocarbons (alkanes, alkenes...), aromatic compounds.