C-10-Q076mediumsingle_mcqHgS+O2→Δ?\mathrm{HgS + O_2 \xrightarrow{\Delta} ?}HgS+O2Δ? (auto-reduction)aHg+SO2\mathrm{Hg + SO_2}Hg+SO2bHgO+S\mathrm{HgO + S}HgO