Hannah is comparing a rock from a riverbed and a rock from deep underground. One is very smooth, and the other has very rough edges. Explain why each rock was probably found in that location

The rock found in the riverbed has been smoothed over by the constant passage of water over time which has smoothed out the rock.

The Rock found deep underground has rough edges as it was formed by breaking from a larger rock fragment which formed by the cooling of magma and therefore has jagged edges like crystals

The rock from the riverbed is smooth because as it interacts with the water and rolls down the current it looses any rugged edges!