Metallic gold frequently is found is aluminosilicate rocks and it is finely dispersed among other minerals it may be extracted by treating the crushed rock with aerated potassium cyanide solution. During this process metallic gold is slowly converted to `[Au(CN)_(2)]^(-)`, which is soluble in water. After equilibrium has been reached, the aqueous is pumped off and the metallic gold is recovered form it by reacting the gold complex with zinc, which is converted to `[Zn(CN)_(4)]^(2-)` . Gold in nature is frequently alloyed with silver which is also oxidised by aerated sodium cyanide solution. Silver occurs as native as well as sulphurised ore. The correct reaction involved in the leaching of gold with dilute solution of NaCN is :A. `4Au+8CN^(-)+2H_(2)O+O_(2)"(air)" rarr4[Au(CN)_(2)]^(-)+4OH^(-)`B. `Au+2CN^(-) rarr Au[(CN)_(2)]^(-)`C. `Zn+2CN^(-) rarr Zn[(CN)_(2)]^(-)`D. `Zn+4CN^(-) rarr Zn[(CN)_(4)]^(-)`