To protect an instrument from an external magnetic field,it is completely surrounded by:

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 :

Magnetic susceptibility of $Mg$ at $300 \ K$ is $1.2 \times 10^{-5}$. What is its susceptibility at $200 \ K$?

If $\chi$ is the magnetic susceptibility and $\mu_{r}$ is the relative permeability of a ferromagnetic substance,then:

The resultant force acting on a diamagnetic material in a non-uniform magnetic field is in the direction . . . . . . .

If $\chi_1$,$\chi_2$,and $\chi_3$ are the magnetic susceptibilities of a paramagnetic material at temperatures $T_1 \ K$,$T_2 \ K$,and $T_3 \ K$ respectively,then which of the following relations is correct?