The correct order of magnetic moments (spin only values in B.M.) is:

Options

A $\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-} \gt$ \left[\mathrm{MnCl}_{4}\right]^{2-} \gt $\left[\mathrm{CoCl}_{4}\right]^{2-}$
B $\left[\mathrm{MnCl}_{4}\right]^{2-} \gt$ \left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-} \gt $\left[\mathrm{CoCl}_{4}\right]^{2-}$
C $\left[\mathrm{MnCl}_{4}\right]^{2-} \gt$ \left[\mathrm{CoCl}_{4}\right]^{2-} \gt $\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}$
D $\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-} \gt$ \left[\mathrm{CoCl}_{4}\right]^{2-} \gt \left[\mathrm{MnCl}_{4}\right]^{2-} $(Atomic nos. :$ \mathrm{Mn}=25, \mathrm{Fe}=26, \mathrm{Co}=27)

C. $\left[\mathrm{MnCl}_{4}\right]^{2-} \gt$ \left[\mathrm{CoCl}_{4}\right]^{2-} \gt $\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}$

Number of unpaired electrons in central atom

\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-},\left[\mathrm{CoCl}_{4}\right]^{2-},\left[\mathrm{MnCl}_{4}\right]^{2-}

zer three five The greater the number of unpaired electrons, the higher the value of magnetic moment