The correct answer is - B. erosion.
The mining is almost always causing a lot of damage in the region where it takes place. The surface mining means the removal of large amounts of soil of the surface. That results in large scale erosion on the already heavily damaged ground. Even when the mining is finished and the region left, it is very hard and very slow process of recuperation, as there's lot of damage done to the soil by the mining and the erosion. The land is barren and totally destroyed, so it needs a lot of time to create a nice texture and structure so that vegetation develops again and stop the further erosion.
