Question

question 3 of 20
which descriptions are examples of fossils?
bones of a cow found lying in a modern field
bones of a saber - toothed cat preserved in rock
burrows of prehistoric clams filled in with ancient mud
imprint of a fern left in ancient sandstone
arrowheads found at an archaeological site

Explanation:

Fossils are remains/traces of ancient organisms preserved in geologic materials. Cow bones in a modern field are recent; arrowheads are human-made artifacts, not fossils. The other three are ancient organism remains/traces in geologic deposits.

Answer:

bones of a saber-toothed cat preserved in rock, burrows of prehistoric clams filled in with ancient mud, imprint of a fern left in ancient sandstone