C analysis: Loess Plateau, located between Taihang Mountain, Qilian Mountain, Great Wall and Qinling Mountain, covers an area of about 500,000 square kilometers. It is the most widely distributed area of loess in the world. Long-term soil erosion has formed the surface morphology of the plateau. The measures to control soil erosion in the Loess Plateau are: planting trees, building terraces, leveling the land and repairing horizontal terraces. Returning farmland to forests and grasslands, repairing earth dams and reservoirs, etc. Among them, building reservoirs, leveling land and leveling terraces are engineering measures. Therefore, C. Comments: The measures taken to investigate soil erosion in the Loess Plateau are more effective.