Fact 1: Carbon may be stored in sedimentary rock for millions of years.

Fact 2: Limestone is a rock composed of calcium, carbon and oxygen.

Given the two facts above, answer the question "what is in limestone?" with the following options: 
- abrasion
 - fossils
 - an anion
 - acid
 - nitrogen
 - gypsum
 - carbon
 - NaCl


 

       carbon  