Answer:
Coal and petroleum.
Step-by-step explanation:
Coal and petroleum are the two examples that can be converted into fossil fuel after being buried under pressure for a long period of time. Both coal and petroleum formed underground with the presence of very high temperature and pressure. Coal is formed when the plant material is placed under high temperature and pressure for thousand of years while on the other hand, petroleum formed when dead bodies of animals are present underground for a very long time with a suitable pressure and temperature turn into petroleum.