ANS:C - perpendicular to equipotential lines

During seepage through a soil, the direction of seepage is always perpendicular to the equipotential lines. Equipotential lines represent lines of equal hydraulic head or potential energy within the soil mass. Water flows from regions of higher hydraulic head to regions of lower hydraulic head. Since water tends to move from areas of higher potential energy to areas of lower potential energy, the direction of seepage is perpendicular to the equipotential lines. Therefore, the correct statement is: "perpendicular to equipotential lines."