Rocks were dissolved by water. Lava deposited and then cooled. The remains of plants and animals were trapped. Air, water, and minerals combined.
I gave my students this multiple choice question: Gas and oil come from deposits of petroleum deep within the earth. What caused these deposits to form?

Only one answer is correct among these 4 choices:
- Rocks were dissolved by water.
- Lava deposited and then cooled.
- The remains of plants and animals were trapped.
- Air, water, and minerals combined.

Could you tell me which one is correct?

The remains of plants and animals were trapped.