Fact 1: Acavern is formed by carbonic acid in groundwater seeping through rock and dissolving limestone.

Fact 2: Any time water and carbon dioxide mix, carbonic acid is the result.

Given the two facts above, answer the question "Which of the following added to groundwater creates caverns?" with the following options: 
- a solute
 - permineralization
 - calcite
 - storing water
 - flooding
 - salinity
 - carbon dioxide
 - heating liquids


 

       carbon dioxide  