Rivers once flowed through the area. Volcanoes were once active in the area. The ocean shoreline once reached this area. Floods were a common occurrence in this area.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Scientists dig in a dry area at the bottom of a mountain range. Fossilized shells of freshwater mussels are found in the area. Which is a likely conclusion that scientists will draw based on this evidence?
Possibilities:
- Rivers once flowed through the area.
- Volcanoes were once active in the area.
- The ocean shoreline once reached this area.
- Floods were a common occurrence in this area.

Rivers once flowed through the area.