Which of the following statements is INCORRECT for diamagnetic...

For diamagnetic materials, the magnetic susceptibility ($\chi$) is small and negative. This implies statement b is correct and statement d is incorrect.

The relative permeability ($\mu_r$) is related to susceptibility by $\mu_r = 1 + \chi$. Since $\chi$ is small and negative, $\mu_r$ is slightly less than $1$. This implies statement a is correct.

Diamagnetism arises due to the inherent orbital motion of electrons in atoms and is practically unaffected by the thermal agitation. Therefore, the magnetic susceptibility of diamagnetic materials is independent of temperature. This implies statement c is correct.

Thus, the only incorrect statement is d, which corresponds to option 1.

Answer: d