Answer:
The correct answer is option A (Dead plants and animals).
Step-by-step explanation:
Fossil fuels are hydrocarbon-containing materials like natural gas, fuel oil, coal which act as a source of energy. These fossil fuels are formed from the remains of dead animals and plants of Carboniferous Period about 360 to 286 million years ago.
At that time the remains of plants and animals along with micro-organisms were decayed which were later covered by sand and silt and trapped it under the rocks. Over time heat and pressure compressed it and changed it into coal, oil and some trapped pockets of gases known as natural gas.
Thus, option A (Dead plants and animals) is the correct answer.