AIIMS 2018 Physics Magnetic Materials MCQ Question

When a magnetic material is placed in a non-uniform magnetic field, it experiences a force due to the gradient of the magnetic field strength (H). The force $F$ on the material can be expressed as $F = m \mu_0 \frac{dB}{dz}$, where $m$ is the magnetic moment of the material and $\mu_0$ is the permeability of free space. Option A accurately reflects this relationship, while the other options incorrectly multiply the expression by factors that do not correspond to the physical principles governing the interaction between the magnetic material and the magnetic field gradient.