Fact 1: Avalley is formed by a river flowing.

Fact 2: Rivers erode the rocks they flow over.

Given the two facts above, answer the question "What is created when rocks erode?" with the following options: 
- calcite
 - A pond
 - A valley
 - detritus
 - fossil fuels
 - A river
 - A volcano
 - a prism


 

   A valley      