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

### Question:
Which is the best evidence that rocks found deep underground were once exposed at the surface?

### Choices:
A. The rocks have been melted by a magma.
B. The rocks have been broken by faults.
C. The rocks have been weathered by water.
D. The rocks have been folded by pressure.

### Answer:
