Match Column-$I$ with Column-$II$.

Column-$I$	Column-$II$
$P$. Nitriding	$I$. Process of heating steel to redness and then cooling it very slowly
$Q$. Annealing	$II$. Process of heating steel in presence of $NH_3$ and producing hard coating of Iron Nitride on the surface of steel
$R$. Tempering	$III$. Process of heating steel to redness and then cooling it suddenly by plunging it into water or oil
$S$. Quenching	$IV$. Process of heating quenched steel to a temperature well below redness and then cooling it slowly

• A
  $P-II, Q-I, R-III, S-IV$
• B
  $P-II, Q-I, R-IV, S-III$
• C
  $P-I, Q-II, R-IV, S-III$
• D
  $P-I, Q-II, R-III, S-IV$