1. The problem asks how farmers can conserve soil and keep it useful year after year. 2. Important rules for soil conservation include: - Planting crops in ways that reduce soil erosion. - Avoiding removal of trees that protect soil. - Using crop rotation to maintain soil nutrients. 3. Evaluate each option: - A. Planting crops in long, straight rows can increase soil erosion because water runs straight down and carries soil away. - B. Cutting down trees from the edges of fields removes natural barriers that protect soil from wind and water erosion. - C. Planting crops in curved rows on sloped land (contour farming) helps slow water runoff and reduces soil erosion. - D. Changing crops from one year to the next (crop rotation) helps maintain soil fertility and reduces pests. 4. Therefore, the correct answers are C and D. Final answer: C and D