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

Question

$(a)\;[Cr(CN)_6]^{-3}\qquad(b)\;[Mn(CN)_6]^{-3}\qquad(c)\;[Fe(CN)_6]^{-3}\qquad(d)\;[CO(CN)_6]^{-3}$