What is the substance added during the extraction of metals that combines with impurities to form a molten product called?

In the extraction of silver,the following reactions take place:
$Ag_2S + NaCN \rightarrow A$
$A + Zn \rightarrow B$
If $B$ is a metal,identify $A$ and $B$.

Pure $O_2$ instead of air is used to oxidise the pig iron because

Which of the following fluxes is used to remove acidic impurities during metallurgy?

The reactions which occur in a blast furnace at $500-800 \ K$ during the extraction of iron from haematite are:
$(i)$ $3 Fe_2O_3 + CO \rightarrow 2 Fe_3O_4 + CO_2$
$(ii)$ $Fe_2O_3 + 3 C \rightarrow 2 Fe + 3 CO$
$(iii)$ $Fe_3O_4 + 4 CO \rightarrow 3 Fe + 4 CO_2$
$(iv)$ $Fe_2O_3 + CO \rightarrow 2 FeO + CO_2$

For the formation of which compound in the Ellingham diagram does $\Delta G^{\circ}$ become more and more negative with an increase in temperature?