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

Fact 2: Fossils are evidence of prehistoric life that is preserved in rock.

Given the two facts above, answer the question "Prehistoric life is preserved in rock when what covers the remains over time?" with the following options: 
- Plant growth is reduced
 - an amoebae
 - layers of sediment
 - single-celled organisms
 - loose soil
 - layers of fungus
 - layers of bone
 - layers of mucus


 

   layers of sediment      