List the properties of magnetic field lines.

(N/A) The properties of magnetic field lines are as follows:
$(a)$ Magnetic field lines emerge from the north pole and merge at the south pole outside the magnet.
$(b)$ The direction of magnetic field lines inside the magnet is from the south pole to the north pole.
$(c)$ Magnetic field lines are closed continuous curves.
$(d)$ No two magnetic field lines can intersect each other because if they did,there would be two directions of the magnetic field at the point of intersection,which is impossible.
$(e)$ The relative strength of the magnetic field is shown by the degree of closeness of the field lines.