Arrange the following complexes in the increasing order of their spin only magnetic moment (in B.M) I. $\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{4-}$ II. $\left[\mathrm{MnCl}_4\right]^{2-}$ III. $\left[\mathrm{Mn}(\mathrm{CN})_6\right]^{4-}$ IV. $\left[\mathrm{Cr}\left(\mathrm{NH}_3\right)_6\right]^{3+}$

• A

  $\mathrm{II} < \mathrm{IV} < \mathrm{I} < \mathrm{III}$
• B

  III $ < $ II $ < $ I $ < $ IV
• C

  $\mathrm{I} < \mathrm{IV} < \mathrm{II} < \mathrm{III}$
• Correct answer
  D

  $\mathrm{I} < \mathrm{III} < \mathrm{IV} < \mathrm{II}$

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