Cast iron is used for the manufacture of

Extraction of gold $(Au)$ involves the formation of complex ions $X$ and $Y$ as shown in the reaction: $\text{Gold ore}$ $\xrightarrow{CN^-, H_2O, O_2} HO^- + X$ $\xrightarrow{Zn} Y + Au$. $X$ and $Y$ respectively are:

Extraction of a metal $(M)$ from its sulfide ore $(M_2S)$ involves the following chemical reactions:
$2M_2S + 3O_2 \xrightarrow{\text{heat}} 2M_2O + 2SO_2 \uparrow$
$M_2S + 2M_2O \xrightarrow{\text{heat}} 6M + SO_2 \uparrow$
The metal $(M)$ may be

Flux is used to remove

In the alumino-thermite process,$Al$ acts as:

Which one of the following oxides is reduced by water gas to obtain the metal during its extraction?