Which one of the following cyano complexes would exhibit the lowest value of paramagnetic behaviour?

(Given: atomic numbers, Cr= 24, Mn= 25, Fe= 26 and Co= 27)

The electronic configurations of the central atoms are as follows:

${ }_{26}{\mathrm{Fe}}^{3+}\left(3\mathrm{d}{)}^5{;}_{27}{\mathrm{Co}}^{3+}\right(3\mathrm{d}{)}^6{;}_{24}{\mathrm{Cr}}^{3+}(3\mathrm{d}{)}^3{;}_{25}{\mathrm{Mn}}^{3+}$

Their configurations in the complexes are as follows:

The complex ${\left[\mathrm{Co}(\mathrm{CN}{)}_6\right]}^{3-}$ does not possess any unpaired electrons and hence will be diamagnetic, i.e., it will exhibit the lowest paramagnetism.