A solution containing 2.675 g of ${\mathrm{CoCl}}_3.6{\mathrm{NH}}_3$ (molar mass = 267.5 g $mo{l}^{-1}$) is passed through a cation exchanger. The chloride ions obtained in solution were treated with excess of ${\mathrm{AgNO}}_3$ to give 4.78 g of AgCl (molar mass = 143.5 g ${\mathrm{mol}}^{-1}$). The formula of the complex is (Atomic mass of Ag = 108 u) 

• A

  $\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3$

• B

  $\left[{\mathrm{CoCl}}_2{\left({\mathrm{NH}}_3\right)}_4\right]\mathrm{Cl}$

• C

  $\left[{\mathrm{CoCl}}_3{\left({\mathrm{NH}}_3\right)}_3\right]$

• D

  $\left[\mathrm{CoCl}{\left({\mathrm{NH}}_3\right)}_5\right]{\mathrm{Cl}}_2$