Consider the following metallurgical processes:
$I$. Heating impure metal with $CO$ and distilling the resulting volatile carbonyl (b.p. $43 \ ^oC$) and finally decomposition at $150 \ ^oC - 200 \ ^oC$ to get the pure metal.
$II$. Heating the sulphide ore in air until a part is converted to oxide and then further heating in the absence of air to let the oxide react with unchanged metal sulphide.
$III$. Electrolysis of the molten electrolyte containing approximately equal amounts of the metal chloride and $NaCl$ to obtain the metal.
The processes used for obtaining magnesium,nickel and copper are respectively:

• A
  $I, II$ and $III$
• B
  $II, III$ and $I$
• C
  $III, I$ and $II$
• D
  $II, I$ and $III$