Remember when we draw magnetic field lines, we draw them so that the density of the lines in a given drawing represents the strength of the field at every location in the drawing. Therefore, if we draw a surface in a uniform magnetic field: a. the number of magnetic field lines must equal the number of electric field lines.
b. the number of magnetic field lines entering the surface must be less than the number leaving the surface.
c. the number of magnetic field lines entering the surface must be greater than the number leaving the surface.
d. the number of magnetic field lines entering the surface must be equal to the number leaving the surface.