Which two examples may be converted into fossil fuel after being buried under pressure for a long period of time

Correct answer: B) Plants and C). Animal Waste
Fossil fuel is formed by a different number of way, but the most commonly they are formed when animals and plants die and are buried under slit, mud and in the soil.
They are formed by the dead and decayed material that is converted to natural gas, coal, and crude oil when they are exposed to heat and high pressure in the crust over millions of years.