The chemical formula of magnetite is .

$\mathrm{A}$: ${\mathrm{Fe}}_2{\mathrm{O}}_3$

$\mathrm{B}$: $\mathrm{FeO}$

$\mathrm{C}$: ${\mathrm{Fe}}_3{\mathrm{O}}_4$

Enter your correct answer as $\mathrm{A}, \mathrm{B},$ or $\mathrm{C}$.

Give one word or a phrase for the following statement:

• Electrode used as a cathode in electrorefining of impure copper.

Extraction of mercury from cinnabar is achieved by:

Cinnabar is heated in air which converts it into:

Among the following which metal is not refined by liquation?