The correct answer is option 4, terracing. Terracing is a method of soil conservation that involves cutting the mountain slope into steps or terraces. This helps to reduce erosion and prevent the loss of soil from sloping land. By creating flat or gently sloping surfaces, terracing helps to slow down the flow of water down the slope and allows it to be absorbed by the soil. It also helps to prevent the formation of gullies and reduces the risk of landslides. Terracing is commonly used in hilly or mountainous regions where agriculture is practiced on slopes. This method helps to make the land more suitable for cultivation and prevents soil erosion, promoting sustainable land use and conservation.