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

Fact 2: Limestones are a common type of sedimentary rock.

Given the two facts above, answer the question "What may be stored in limestone for millions of years?" with the following options: 
- dark matter
 - chemicals
 - still-living organisms
 - nothing
 - fossils
 - matter
 - carbon
 - Energy


 

       carbon  