The plant described has many broad leaves with rough edges. Referring to the dichotomous key:
- It falls under 1b (Leaves are broad), so we go to 2.
- For 2b, it has many leaves, so we go to 4.
- Going to 4b, since the leaflet edges are rough, the answer is Juglans nigra.
Therefore, the correct response is juglans nigra.