I think it will be B. Hope it helps :)
Answer: alright now listen fe203(s)=567.66666
Explanation:
Formula: NA2S2O3. Valency: 2
Explanation:
Mg+O>MgO
Here the mg loses it electron and is oxidised and oxygen gains and is reduced.
Mg(2+)and O(2-)
Mg is a reducing agent it makes oxygen to be reduced while itself being oxidised and vice versa.