The magnetic susceptibility is negative for

Identify the incorrect statement from the following.

Magnets cannot be made from which of the following substances?

Statement $I :$ The ferromagnetic property depends on temperature. At high temperature,a ferromagnet becomes a paramagnet.
Statement $II :$ At high temperature,the domain wall area of a ferromagnetic substance increases.
In the light of the above statements,choose the most appropriate answer from the options given below :

If $\chi$ stands for the magnetic susceptibility of a substance, $\mu$ for its magnetic permeability, and $\mu_0$ for the permeability of free space, then which of the following is correct?

Explain quantitatively the order of magnitude difference between the diamagnetic susceptibility of ${N_2} \left( { \sim 5 \times {{10}^{ - 9}}} \right)$ (at $STP$) and ${Cu} \left( { \sim {{10}^{ - 5}}} \right)$.