Which pair of isomers illustrates the concepts of ionization isomers ? 

• A

  ${\left[\mathrm{Cr}\left(\mathrm{SCN}\right){\left({\mathrm{NH}}_3\right)}_5\right]}^{2+}\text{ and }{\left[\mathrm{Cr}\left(\mathrm{NCS}\right){\left({\mathrm{NH}}_3\right)}_5\right]}^{2+}$

• B

  $\left[\mathrm{CoCl}{\left({\mathrm{NH}}_3\right)}_5\right]{\mathrm{SO}}_4\text{ and }\left[\mathrm{Co}\left({\mathrm{SO}}_4\right){\left({\mathrm{NH}}_3\right)}_5\right]\mathrm{Cl}$

• C

  $\text{ cis }\left[{\mathrm{PtCl}}_2{\left({\mathrm{NH}}_3\right)}_2\right]\text{ and trans }\left[{\mathrm{PtCl}}_2{\left({\mathrm{NH}}_3\right)}_2\right]$

• D

  $(+)-{\left[\mathrm{Co}(en{)}_3\right]}^{3+}\text{ and }(-){\left[\mathrm{Co}(en{)}_3\right]}^{3+}$