Here's a problem to solve: Two layers of sedimentary rock are exposed on the side of a hill. Only one of the layers has fossils. The lack of fossils in one layer of sedimentary rock is most likely due to

Among the 4 following options, which is the correct answer?

- A: changing environments.
 
- B: volcanic activity.
 
- C: changing rates of erosion.
 
- D: evaporation of sea water.
 