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?

  Options: 
 A. Rivers once flowed through the area.
 B. Volcanoes were once active in the area.
 C. The ocean shoreline once reached this area.
 D. Floods were a common occurrence in this area.
Answer: A