The reaction of aqueous $[Ni(H_2O)_6]^{2+}$ is performed by the addition of a bidentate ligand ethane-$1,2$-diamine $(en)$. Match the following:

$[Ni(H_2O)_6]^{2+} : en$ molar ratio	Colour of the product
$A. 1:1$	$I. \text{Pale blue}$
$B. 1:2$	$II. \text{Blue/Purple}$
$C. 1:3$	$III. \text{Violet}$

The correct match is:

• A

  $A-I, B-II, C-III$

• B

  $A-II, B-III, C-IV$

• C

  $A-III, B-I, C-II$

• D

  $A-IV, B-I, C-III$