How are fossils used to determine the relative ages of rocks?

A. Fossils can only be found in rocks that formed before the organism died, so rocks with newer fossils in them are older than rocks with older fossils.

B. Fossils can only be found in rocks that formed after the organism died, so rocks with newer fossils in them are younger than rocks with older fossils.

C. Rocks cannot be dated according to their fossils, but the age of fossils can be determined from the age of the rock they are in.

D. Rocks and fossils do not reveal any information about each other’s age.