While standing near a river, a student noticed small rocks colliding with larger rocks, causing small pieces to break off and be carried downstream. What processes is the student observing?
A. The small rocks are chemically weathering the larger rocks and erosion is moving the pieces downstream.
B. The small rocks are chemically weathering the larger rocks and deposition is moving the pieces downstream.
C The small rocks are mechanically weathering the larger rocks and erosion is moving the pieces downstream.
D. The small rocks are mechanically weathering the larger rocks and deposition is moving the pieces downstream.