Fact 1: Fossils are formed when layers of sediment cover the remains of organisms over time.

Fact 2: Natural gas is a fossil fuel.

Given the two facts above, answer the question "What is formed from layers of sediment covering the remains of organisms over time?" with the following options: 
- metal
 - cold
 - rings
 - coral reef
 - sea urchins
 - natural gas
 - exoskeleton
 - shells


 

      natural gas   