Step-by-step explanation:
In the given problem, Jill uses a magnet to pick up a nail. Then, she touches the nail to a paper clip and picks up the paper clip.
Magnetic field lines are the area around the magnet in which the magnetic force can be experienced.
A nail is attracted towards the magnet when it comes under the influence of the magnetic field. The domains of the nail gets aligned in the direction of the magnetic field. The nail will act as a magnet. It acquires some property of the magnet and behaves as a temporary magnet.
When Jill pulls the magnet away from the nail then the paper will fall as the iron will lose its magnetism.