Question

which descriptions are examples of fossils?
bones of a saber - toothed cat preserved in rock
bones of a cow found lying in a modern field
dinosaur tracks preserved in the remains of a riverbed
arrowheads found at an archaeological site
imprint of a fern left in ancient sandstone

Explanation:

Fossils are the preserved remains or traces of ancient organisms. The bones of a saber - toothed cat preserved in rock are from an ancient animal. Dinosaur tracks are traces of a dinosaur (an ancient organism). The imprint of a fern in ancient sandstone is the preserved remains of an ancient plant. The bones of a cow in a modern field are from a recent organism. Arrowheads at an archaeological site are human - made artifacts, not fossils.

Answer:

bones of a saber - toothed cat preserved in rock, dinosaur tracks preserved in the remains of a riverbed, imprint of a fern left in ancient sandstone.