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

### Question:
A researcher found shark fossils on top of a mountain. This evidence suggests which of the following about this region?

### Choices:
A. It was once below a waterfall.
B. It was once part of a riverbed.
C. It was once covered by an ocean.
D. It was once near a freshwater lake.

### Answer:
