If the same index fossils are found in two separate rock layers, the two rock layers most likely ...

A. reveal a disconformity.

B. reveal a nonconformity.

C. were formed at the same time.

D. were formed at different times.

I think the correct answer from the choices listed above is option C. If the same index fossils are found in two separate rock layers, the two rock layers most likely were formed at the same time. Index fossils are fossils used to define and identify geologic periods (or faunal stages). Hope this answers the question.