Final answer:
The three principal fossil fuels are coal, oil, and natural gas.
Step-by-step explanation:
The three principal fossil fuels are: coal, oil, and natural gas. These fuels are formed from the buried remains of ancient plants and animals that have undergone chemical changes over millions of years. Coal is formed from the remains of plant material, while oil and natural gas are formed from the remains of marine organisms.
Learn more about Fossil fuels