Rocks have many scratches. Rocks contain fossils. Rocks are covered by moss. Rocks are deep underground.
I gave my students this multiple choice question: Rocks sometimes show evidence of ancient glaciers. Which is the best sign that glaciers once covered an area?

Only one answer is correct among these 4 choices:
- Rocks have many scratches.
- Rocks contain fossils.
- Rocks are covered by moss.
- Rocks are deep underground.

Could you tell me which one is correct?

Rocks have many scratches.