Answer: D) The field lines around a magnet point from the north pole to the south pole to show the direction of the magnetic force on the monopole.
Step-by-step explanation:
A magnet has two poles: North pole and south pole. Monopole do not exist. In a magnet, domains of atoms oriented in a single direction exist. Magnetic field lines start from North pole and enter south pole.
If a monopole existed, it would be used to describe the magnetic field lines as the field lines around a magnet point from the north pole to the south pole to show the direction of the magnetic force on the monopole. Hence, the correct option is D.