. . . . . . . . at a point may be defined as equal to the lines of force passing normally through a unit cross section at that point.

The correct answer is: C. Electric flux

Electric flux is the measure of the electric field lines that pass through a surface. It is defined as the number of electric field lines that pass through a unit area of a surface perpendicular to the field lines.

Electric intensity is the force per unit charge that would be experienced by a test charge placed in an electric field.

Magnetic flux density is the measure of the magnetic field lines that pass through a surface. It is defined as the number of magnetic field lines that pass through a unit area of a surface perpendicular to the field lines.

None of the above is the correct answer because it does not define electric flux.