Choose the correct option: 

Magnetic field lines ______________ .

Magnetic field lines cannot intersect at all.

Tangent on magnetic field lines gives the direction of the magnetic field.
If the magnetic field lines intersect at any point, then at the point of intersection, two tangents can be drawn which will give two different directions of the field at that point. This is contradictory.
So, magnetic field lines can not intersect each other.