Concept:Surface irrigation spreads water by gravity over the soil surface. The question asks for the option that is NOT part of surface irrigation.Explanation:Natural flooding and check flooding are both traditional surface irrigation methods. Sprinkler irrigation is a separate, pressurised technique, but it still supplies water to crops. Mole drainage is completely different: it is a subsurface drainage system used to remove excess water from clay soils. Drainage is the opposite of irrigation, so mole drainage is not related to surface irrigation at all.Answer:A. Mole drainage