Which of the following statements is true in respect of diamagnetic susbtances?

Magnetic hysterisis is exhibited by ............ magnetic materials

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

The Curie temperature of cobalt and iron are $$1400 \mathrm{~K}$$ and $$1000 \mathrm{~K}$$ respectively. At $$T=1600 \mathrm{~K}$$, the ratio of magnetic susceptibility of cobalt to that of iron is