The correct answer is: C. potential gradient.
Electric intensity is the force per unit charge acting on a test charge placed in an electric field. It is a vector quantity, with its direction being the same as the direction of the electric field. The electric field strength is equal to the negative of the gradient of the electric potential. This means that the electric field strength is greatest at points where the electric potential is changing most rapidly.
Electric flux is the total amount of electric field passing through a surface. It is a scalar quantity, and its value is equal to the integral of the electric field over the surface.
Magnetic flux density is the amount of magnetic field passing through a surface. It is a vector quantity, with its direction being the same as the direction of the magnetic field. The magnetic flux density is equal to the permeability of the medium times the magnetic field strength.
None of the above options are equal to electric intensity.