Which of the following step of metallurgy requires oxygen?

Roasting of cinnabar and Leaching of gold by $\mathrm{NaCN}$ solution involving step of metallurgy requires oxygen.

Roasting a metal ore normally leads in the conversion of the metal to the oxide, however roasting cinnabar, $\mathrm{HgS}$, produces metallic mercury rather than an oxide of mercury. The following reaction is obtain.

$\mathrm{HgS}\to \mathrm{HgO}\to \mathrm{Hg}$

Leaching agents like diluted $\mathrm{NaCN}$ are employed in the extraction of gold. The transformation of gold into a cyanide complex allows for a later replacement extraction of the metal.

Leaching of gold involve following reaction,

$4Au\left(s\right)+8NaCN\left(aq\right)+H_{2}O+O_2\to 4Na\left[Au\right(CN{)}_2]+4KOH$

Hence, option B and D are correct.