prevent a collapse of the underlying sediment. limit the types of pollutants that can enter the soil. increase water absorption by the replaced sediments. reduce soil erosion and provide new habitat for animals.
I gave my students this multiple choice question: When mining for coal, a mining company removes the plants and layers of soil and rock above the coal deposit, and takes the coal. When the operation is complete, the mining company returns soil and rock, covers it with a layer of topsoil, and plants trees and grass. The trees and grass help to

Only one answer is correct among these 4 choices:
- prevent a collapse of the underlying sediment.
- limit the types of pollutants that can enter the soil.
- increase water absorption by the replaced sediments.
- reduce soil erosion and provide new habitat for animals.

Could you tell me which one is correct?

reduce soil erosion and provide new habitat for animals.