A
Below is a question with multiple-choice answers. Choose the correct option based on your reasoning.

### Question:
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

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

### Answer:
