Answer: Closed continuous loops.
- A Open curves ending at poles
- B Closed continuous loops
- C Straight radial lines
- D A single point
Correct answer: B. Closed continuous loops
Explanation: Magnetic field lines are always closed loops; outside they run from N to S and continue inside from S to N, since isolated poles do not exist.
Magnetic field of a bar magnet: field lines emerge from the north pole and re-enter at the south pole outside the magnet, forming continuous closed loops. Image: Geek3, CC BY-SA 3.0, via Wikimedia Commons.
Concept context
Bar magnets, Earth's magnetism, and how different materials respond to an external magnetic field - diamagnetic, paramagnetic, and ferromagnetic behaviour.