What is the process of leaching also known as?

For the purification of alumina,the modern processes most useful when $(i)$ the impurity present is a lot of iron oxides and $(ii)$ the impurity present is a lot of silica,are:

The correct statements regarding the froth floatation method in metallurgy are:
$I$. Used for the purification of sulphide ores
$II$. Used for the roasting of sulphide ores
$III$. It is based on the relative densities of gangue and ore particles
$IV$. It is based on the difference in the wetting properties of gangue and ore particles in frothing agent and water

Collectors are the substances which help in attachment of an ore particle to air bubble in froth. $A$ popular collector used industrially is

Explain the froth flotation process.

The metal extracted by leaching with a cyanide is