The fish migrated from the ocean The fish was unable to reproduce A mountain used to be in this area A river used to run through this area
I gave my students this multiple choice question: What is the best conclusion that can be made upon discovering a fossil of a freshwater fish in a desert area?

Only one answer is correct among these 4 choices:
- The fish migrated from the ocean
- The fish was unable to reproduce
- A mountain used to be in this area
- A river used to run through this area

Could you tell me which one is correct?

A river used to run through this area