A type of trilobite is used as an index fossil. These fossils were made around 540 million years ago. A scientist finds a trilobite fossil within layer 3 in the diagram (picture).

What can the scientist conclude from this finding?

A. Fossils from layer 9 are the newest in the diagram.

B. All the fossils in this diagram are at least 540 million years old.

C. Layer 1 has the newest fossils in the diagram.

D. Fossils in layer 5 are less than 540 million years old.