Concept:Infiltration is the downward movement of water into the soil, largely controlled by the permeability of the soil or rock material.Explanation:The rate of infiltration into the sub-soil depends mainly on how easily water can pass through the soil and underlying rock layers. This is determined by the nature of the rocks, including porosity, permeability, and texture. Rainfall intensity and slope affect surface runoff, but the nature of the rocks is the major factor controlling infiltration into the sub-soil.Answer:C. nature of rocks