In the extraction of $Zn$,which gas is burnt in the jackets surrounding the retorts?

Upon heating with $Cu_2S$,the reagent$(s)$ that give copper metal is/are:
$(A)$ $CuFeS_2$
$(B)$ $CuO$
$(C)$ $Cu_2O$
$(D)$ $CuSO_4$

Given below are two statements.
Statement $I$: According to the Ellingham diagram,any metal oxide with higher $\Delta G^{\circ}$ is more stable than the one with lower $\Delta G^{\circ}$.
Statement $II$: The metal involved in the formation of oxide placed lower in the Ellingham diagram can reduce the oxide of a metal placed higher in the diagram.
In the light of the above statements,choose the correct answer from the options given below.

Native silver metal forms a water soluble complex with a dilute aqueous solution of $NaCN$ in the presence of

Copper is the most noble of the first row transition metals and occurs in small deposits in several countries. Ores of copper include chalcanthite $(CuSO_4 \cdot 5H_2O)$,atacamite $(Cu_2Cl(OH)_3)$,cuprite $(Cu_2O)$,copper glance $(Cu_2S)$ and malachite $(Cu_2(OH)_2CO_3)$. However,$80\%$ of the world copper production comes from the ore of chalcopyrite $(CuFeS_2)$. The extraction of copper from chalcopyrite involves partial roasting,removal of iron and self-reduction. $1.$ Partial roasting of chalcopyrite produces: $(A)$ $Cu_2S$ and $FeO$ $(B)$ $Cu_2O$ and $FeO$ $(C)$ $CuS$ and $Fe_2O_3$ $(D)$ $Cu_2O$ and $Fe_2O_3$. $2.$ Iron is removed from chalcopyrite as: $(A)$ $FeO$ $(B)$ $FeS$ $(C)$ $Fe_2O_3$ $(D)$ $FeSiO_3$. $3.$ In self-reduction,the reducing species is: $(A)$ $S$ $(B)$ $O^{2-}$ $(C)$ $S^{2-}$ $(D)$ $SO_2$. Give the answer for questions $1, 2$ and $3$.

Extraction of metal from the ore cassiterite involves