The correct answer is option (B) planting grass on the slopes.
The soil depletion can be prevented by adding grasses and smaller plants on the slopes. It keeps the soil intact and prevent the soil from getting erode or blown away.
The fertilizers may decrease the quality of the soil due to the presence of the chemicals,, also, the fertilizers are added to enhance the growth of the crop. The dune fences are used to prevent the sand flow in the deserts, it helps in decreasing the shifting of the sand mass due to wind.