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.

• A
  $I, II$ and $III$ are correct.
• B
  Only $I$ and $II$ are correct.
• C
  Only $I$ and $III$ are correct.
• D
  Only $II$ and $III$ are correct.