An aqueous solution of CoCl₂ on addition of excess of concentrated HCI turns blue due to formation of

• A

  $\left[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_4{\mathrm{Cl}}_2\right]$

• B

  ${\left[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_2{\mathrm{Cl}}_4\right]}^{2-}$

• C

  ${\left[{\mathrm{CoCl}}_4\right]}^{2-}$

• D

  ${\left[\mathrm{Co}{\left({\mathrm{H}}_2\mathrm{O}\right)}_2\mathrm{Cl}\right]}_2$