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

Fact 2: Carbon dioxide dissolved in rainwater forms carbonic acid.

Given the two facts above, answer the question "What chemical creates a cavern?" with the following options: 
- carbonic acid
 - heating liquids
 - hydrogen and oxygen
 - aqueous solution
 - salt
 - oxygen
 - hydrogen
 - flow of electrons


 

 carbonic acid        