The correct answer is: B. $B_{\max}^{1.6}$
Hysteresis loss is the energy lost in a magnetic material when the magnetic field is repeatedly reversed. The amount of hysteresis loss is proportional to the square of the maximum flux density, $B_{\max}$. This is because the magnetic domains in the material tend to align with the applied magnetic field, and when the field is reversed, the domains have to move back to their original alignment. This movement of the domains causes friction, which results in heat loss.
The equation for hysteresis loss is:
$P_h = K_h B_{\max}^2$
where $K_h$ is the hysteresis coefficient, which is a property of the material.
The options A, C, and D are incorrect because they do not take into account the square of the maximum flux density.