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

In the given complex Mn is present in +2 oxidation state and has 5 unpaired electrons. Hence, the magnetic moment will be = n(n+2) = 5(5+2) =5.9BM In the given complex Co is present in +2 oxidation state and has 3 unpaired electrons. Hence, the magnetic moment will be = n(n+2) = 3(3+2) =3.9BM In the given complex Fe is present in +2 oxidation state and has no unpaired electrons because of the presence of a strong ligand.. Hence, the magnetic moment will be = n(n+2) =0BM The decreasing order will be 2- 2- 4- 4 4 6 [MnCl ] >[CoCl ] >[Fe(CN) ] Hence, the correct answer is option (a).