The species which possesses the highest spin angular momentum $(S)$ is:

• Correct answer
  A

  $\left[\mathrm{Ni}\left(\mathrm{NH}_3\right)_6\right] \mathrm{Cl}_2$
• B

  $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right] \mathrm{Cl}_2$
• C

  $\left[\mathrm{Fe}\left(\mathrm{NH}_3\right)_6\right] \mathrm{Cl}_2$
• D

  $\left[\mathrm{Cu}\left(\mathrm{NH}_3\right)_6\right] \mathrm{Cl}_2$

Hence, the correct answer is option: 'A'.