Which method is used for the concentration of cassiterite ore?

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

Which of the following is used as a stabilizer during the concentration of sulphide ores?

Difference in density is the basis of

Which of the following metals is extracted by the cyanide process (leaching)?

Wolframite ore is separated from tinstone $(SnO_2)$ by which of the following processes?