TOEFL Listening: TPO-TOEFL听力TPO - 70A1PE99Y2XOH15XR$

Why are nutrients in the soil NOT carried away by spring runoff? A. The roots of shrubs prevent nutrient-filled soil from being washed away. B. Most nutrients are not in the area of the soil most affected by runoff. C. Most nutrients remain frozen in the permafrost when spring runoff is at its peak. D. Most nutrients have been absorbed by vegetation before the runoff period begins.