Which elements of group $6 \mathrm{~A}$ are oxidizing agents and which are reducing agents?
(a) $\mathrm{O}$ and $\mathrm{Se}$ are reducing agents while $\mathrm{S}$ and Te are oxidizing agents.
(b) $\mathrm{O}$ and $\mathrm{S}$ are reducing agents while Se and Te are oxidizing agents.
(c) $\mathrm{O}$ and $\mathrm{S}$ are oxidizing agents while Se and Te are reducing agents.
(d) $\mathrm{O}$ and $\mathrm{Se}$ are oxidizing agents while $\mathrm{S}$ and $\mathrm{Te}$ are reducing agents.