The correct answer is: C. equal to or less than the infiltration capacity.
Infiltration rate is the rate at which water can enter the soil. Infiltration capacity is the maximum rate at which water can enter the soil. Infiltration rate is always equal to or less than infiltration capacity because the soil can only absorb so much water at a time. If water is falling at a rate faster than the soil can absorb it, then the excess water will run off the surface.
Option A is incorrect because infiltration rate is always equal to or less than infiltration capacity.
Option B is incorrect because infiltration rate is always equal to or less than infiltration capacity.
Option D is incorrect because infiltration rate is always equal to or less than infiltration capacity.