Magnetic moment is directly proportional to the number of unpaired in the central metal atom of a complex.
It is calculated by the formula, μ=n(n+2)BM
(A) [FeF6]3−
Fe+3→3d54s0
n=5
(B) [Fe(CN)6]3−

Fe+3→3d54s0
n=1
(C) [MnCl6]3−

Mn+3→3d44s0
n=4
(D) [Mn(CN)6]3−

Mn+3→3d44s0
n=2
Hence,correctorderofmagneticmomentisA>C>D>B