Which of the following ores is concentrated by 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.

The ore that is concentrated by froth floatation process is

Which of the following statements is not correct?
$(i)$ Froth-floatation is used for removing gangue from sulphide ore.
$(ii)$ Cresols are used to stabilise the froth.
$(iii)$ Sodium cyanide can be used as depressant for preferential separation.
$(iv)$ Aniline can be used as froth enhancer.

In the froth floatation process for the purification of ores,the ore particles float because

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