Extraction of gold and silver involves leaching with $\require{mhchem}\ce{CN-}$ ion. Silver is later recovered by
(a) distillation
(b) zone refining
(c) displacement with $\ce{Zn}$
(d) liquation
(a) distillation
(b) zone refining
(c) displacement with $\ce{Zn}$
(d) liquation