Final answer:
The combination of variables that leads to the least erosion would involve a smaller value for the independent variable, fewer years of erosion.
Step-by-step explanation:
In the context of erosion, the independent variable refers to the factor that is being changed or manipulated, while the dependent variable refers to the factor that is being measured or observed. In this case, the independent variable would be 'x', which represents the number of years, and the dependent variable would be 'y', which represents the amount of soil lost per year. So, the combination of variables that leads to the least erosion would be a smaller value of 'x', indicating fewer years of erosion.