Explanation: When a material is exposed to a magnetizing force, it can become magnetized. If some of that magnetism persists even after the external magnetizing force has been removed, this is known as **residual magnetism**. This property is crucial for understanding how permanent magnets work and is a fundamental concept in electromagnetism. * **Reluctance** (A) is the opposition a material offers to the establishment of magnetic flux lines within it, similar to resistance in an electrical circuit. It doesn't describe remaining magnetism. * **Permeability** (C) is a measure of how easily a material can be magnetized. A high permeability material readily allows magnetic flux to pass through it. * **Hysteresis** (D) describes the phenomenon where the magnetic state of a material depends not only on the current applied magnetic field but also on its past magnetic history. Residual magnetism is a manifestation observed within a hysteresis loop, but hysteresis itself is the general behavior, not the specific "remaining force."