The mountain range was once under water. Birds flying overhead dropped the clam shells. Animals released the clam shells in their waste. The clams lived on land before moving to water.
I gave my students this multiple choice question: Fossils of clam shells were found in the Appalachian Mountains. Which of these statements best explains why the clam shells were found in the Appalachian Mountains?

Only one answer is correct among these 4 choices:
- The mountain range was once under water.
- Birds flying overhead dropped the clam shells.
- Animals released the clam shells in their waste.
- The clams lived on land before moving to water.

Could you tell me which one is correct?

The mountain range was once under water.