Question

multiple-choice question
if a scientist finds a fossilized trilobite in a sedimentary rock layer, what does it tell them?
a. that trilobites were time travelers who visited this rock layer for fun.
b. that this area was once covered by an ocean millions of years ago.
c. that a prehistoric pet store once sold trilobites here.
d. that the trilobite had a terrible sense of direction and got stuck.

Explanation:

Trilobites were ancient marine arthropods that lived exclusively in ocean environments millions of years ago. Their fossils are only found in sedimentary rocks formed in aquatic settings, so discovering one indicates the area was once ocean habitat. The other options are fictional and not scientifically valid.

Answer:

B. That this area was once covered by an ocean millions of years ago.