Answer: does not exist.
- A does not exist
- B exists freely
- C is very common
- D is a north pole only
Correct answer: A. does not exist
Explanation: Magnetic poles always occur in north–south pairs; isolated monopoles have never been observed.
Magnetic field lines form closed loops: outside the bar magnet they run from the N pole to the S pole; inside, they continue from S back to N, so the lines never start or end anywhere.
Concept context
Bar magnets, Earth's magnetism, and how different materials respond to an external magnetic field - diamagnetic, paramagnetic, and ferromagnetic behaviour.