Extraction of zinc from zinc blende is achieved by

Tin is obtained from cassiterite by reduction with coke. Use the data given below to determine the minimum temperature (in $K$) at which the reduction of cassiterite by coke would take place.
At $298 \ K$: $\Delta_{f}H^{\circ}(SnO_{2(s)}) = -581.0 \ kJ \ mol^{-1}$,$\Delta_{f}H^{\circ}(CO_{2(g)}) = -394.0 \ kJ \ mol^{-1}$
$S^{\circ}(SnO_{2(s)}) = 56.0 \ J \ K^{-1} \ mol^{-1}$,$S^{\circ}(Sn_{(s)}) = 52.0 \ J \ K^{-1} \ mol^{-1}$
$S^{\circ}(C_{(s)}) = 6.0 \ J \ K^{-1} \ mol^{-1}$,$S^{\circ}(CO_{2(g)}) = 210.0 \ J \ K^{-1} \ mol^{-1}$
Assume that the enthalpies and the entropies are temperature independent.

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

Assertion : Extraction of iron metal from iron oxide ore is carried out by heating with coke.
Reason : The reaction,
$Fe_2O_{3(s)} \to Fe_{(s)} + 3/2 O_{2(g)}$ is a spontaneous process.

Consider the following reactions:
$2 \, XS + 3 \, O_2 \xrightarrow{\Delta} 2 \, XO + 2 \, SO_2$
$2 \, XO + XS \xrightarrow{\Delta} 3 \, X + SO_2$
Then $X$ can not be

Leaching of gold with dilute aqueous solution of $NaCN$ in presence of oxygen gives complex $[A]$,which on reaction with zinc forms the elemental gold and another complex $[B]$. $[A]$ and $[B],$ respectively are ...... .