A magnet produces magnetic field lines. These lines exit one magnet pole and enter the opposite pole. These lines are shaped like circles. These lines produce a magnetic field.

A magnet produces magnetic field lines. Due to several unique characteristics, magnetic field lines are given an excessive amount of importance. Here are a few characteristics of magnetic field lines:
1. The density of magnetic field lines and the strength of the magnetic field are inversely related. It varies in direct proportion to the density of magnetic field lines in a given location.
2. The lines of the magnetic field do not cross.
3. From the North Pole, magnetic field lines radiate toward the South Pole.
4. Magnetic field lines create closed, circular loops.
At every location in space, the magnetic field's direction is perpendicular to the field line.
We can see from the previous description that option (D) defies the characteristics of a magnetic field.

Hence, the correct answer is option D.