Q: What is a thick, dark brown or black liquid found in rock layers of the earth's crust?


Read this paragraph and choose the correct option from the provided answers:

Oil is a thick, dark brown or black liquid. It is found in rock layers of Earth's crust. Oil is currently the most commonly used source of energy in the world.

 Choices:

- propane

- fossil fuel

- coal

- oil


A:
oil