What evidence supports a scientist's conclusion that fossil B is older than fossil A?

A. Fossil A and fossil B were both found at the same depth below Earth's surface. B. Fossil B was found at a depth of 185 meters below Earth's surface, while fossil A was found at a depth of 50 meters below Earth's surface.
C. Fossil B was found at a depth of 50 meters below Earth's surface, while fossil A was found at a depth of 185 meters below Earth's surface.
D. Fossil A was found below Earth's surface, while fossil B was found at surface level.