Ohio was once covered by warm seas. A large glacier once passed over Ohio. The average rainfall in Ohio is now much more than it once was. The average temperature in Ohio is now much warmer than it.
I gave my students this multiple choice question: Corals are animals that live in tropical oceans. Fossils of corals are found in Ohio. What does the presence of coral fossils suggest about how the environment of Ohio has changed over time?

Only one answer is correct among these 4 choices:
- Ohio was once covered by warm seas.
- A large glacier once passed over Ohio.
- The average rainfall in Ohio is now much more than it once was.
- The average temperature in Ohio is now much warmer than it.

Could you tell me which one is correct?

Ohio was once covered by warm seas.