The role of depressants in the Froth Flotation method is to $.....$.

The idea of the froth floatation method came from a person $X$ and this method is related to the process $Y$ of ores. $X$ and $Y$,respectively,are

Observe the following statements regarding the purification of bauxite and select the correct answer.
$I$ : During the Hall's process,silicon is removed in the form of vapor.
$II$ : Bauxite containing $Fe_2O_3$ impurities is purified by the Bayer's process.
$III$ : During the Serpek's process,$AlN$ is formed.

Which of the ores mentioned in the table can be concentrated by the magnetic separation method?

Metal	Ores and Composition
$Aluminium$	$Bauxite: AlO_{x}(OH)_{3-2x} (0 < x < 1)$; $Kaolinite: [Al_{2}(OH)_{4}Si_{2}O_{5}]$
$Iron$	$Haematite: Fe_{2}O_{3}$; $Magnetite: Fe_{3}O_{4}$; $Siderite: FeCO_{3}$; $Iron pyrites: FeS_{2}$
$Copper$	$Copper pyrites: CuFeS_{2}$; $Malachite: CuCO_{3} \cdot Cu(OH)_{2}$; $Cuprite: Cu_{2}O$; $Copper glance: Cu_{2}S$
$Zinc$	$Zinc blende or Sphalerite: ZnS$; $Calamine: ZnCO_{3}$; $Zincite: ZnO$

Copper pyrites are concentrated by

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: