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

Fact 2: When caves contain connecting rooms, they are called caverns.

Given the two facts above, answer the question "What is one element used to create caves?" with the following options: 
- sunlight
 - heat energy
 - Calcium carbonate
 - hydrogen and oxygen
 - calcite
 - carbonic acid
 - less water
 - salinity


 

      carbonic acid   