Fact 1: Flowing water can slowly dissolve carbon in sedimentary rock.

Fact 2: Limestone is a type of sedimentary rock.

Given the two facts above, answer the question "what can flowing water slowly dissolve carbon in?" with the following options: 
- zinc
 - fossil fuels
 - density
 - loose soil
 - precipitation
 - limestone
 - hydrocarbons
 - volume


 

      limestone   