Froth flotation method is useful for the concentration of which of the following ores?

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.

In the froth-floatation process,palm oil functions as:

The function of potassium ethyl xanthate in the froth floatation process is to make the ore

$NaCN$ is sometimes added in the froth flotation process as a depressant when $ZnS$ and $PbS$ minerals are expected because

Which of the following ores is concentrated by the leaching process?