Answer the following question given this paragraph: 

Sediments are small fragments of rocks and minerals. Pebbles, sand, silt, and clay are examples of sediments. Sedimentary rocks may include fossils. Fossils are materials left behind by once-living organisms. Fossils can be pieces of the organism, like bones. They can also be traces of the organism, like footprints.


Q: What is the term for materials that have been left behind by organisms that once lived?


A:
fossils