Among statements $(a)- (d),$ the correct ones are 

$(a)$ Lime stone is decomposed to $CaO$ during the extraction of iron from its oxides.

$(b)$ In the extraction of silver, silver is extracted as an anionic complex.

$(c)$ Nickel is purified by Mond's process.

$(d)$ $Zr$ and $Ti$ are purified by Van Arkel method.

In the extraction of silver, $Ag_2S$ is dissolved in :

Rutile is separated from chlorapatite by

Extraction of gold and silver involves leaching with $CN^-\, ion.$ Silver is later recovered by

In the metallurgical extraction of copper, following reaction is used :

$FeO + SiO _{2} \rightarrow FeSiO _{3}$

$FeO$ and $FeSiO _{3}$ respectively are.