The reaction representing the Mond process for metal refining is ____.

$\displaystyle \mathrm{Zr}+2 \mathrm{I}_2 \xrightarrow{\Delta} \mathrm{ZrI}_4$

$\displaystyle \mathrm{Ni}+4 \mathrm{CO} \xrightarrow{\Delta} \mathrm{Ni}(\mathrm{CO})_4$

$\displaystyle 2 \mathrm{~K}\left[\mathrm{Au}(\mathrm{CN})_2\right]+\mathrm{Zn} \xrightarrow{\Delta} \mathrm{~K}_2\left[\mathrm{Zn}(\mathrm{CN})_4\right]+2 \mathrm{Au}$

$\displaystyle \mathrm{ZnO}+\mathrm{C} \xrightarrow{\Delta} \mathrm{Zn}+\mathrm{CO}$