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

Fact 2: Carbon is the fuel source.

Given the two facts above, answer the question "What may be stored in sedimentary rock for millions of years." with the following options: 
- Sand castles
 - Chemical energy
 - heat energy
 - Millions of dollars.
 - A fuel source.
 - Energy.
 - In sediment
 - Stored animal fur.


 

     A fuel source.    