Which of the following is used as a froth stabilizer in the froth flotation process?

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.

Froth flotation method is used to remove impurities from ore because:

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

Why is the concentration of ore performed?

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: