V^2+ > Cr^2+ > Ru^3+ > Fe^2+
V^2+ > Ru^3+ > Cr^2+ > Fe^2+
Cr^2+ > V^2+ > Ru^3+ > Fe^2+
Cr^2+ > Ru^3+ > Fe^2+ > V^2+
Correct option is A. V^2+ > Cr^2+ > Ru^3+ > Fe^2+
Solution:- (A) V^2+ > Cr^2+ > Ru^3+ > Fe^2+
According to equations, all the complexes are low spin.
Complex Configuration No. of unpaired electrons
[V(CN)_6]^4- t_2g ^3e_g^0 3
[Cr(NH_3)_6]^2+ t_2g ^4e_g^0 2
[Ru(NH_3)_6]^3+ t_2g ^5e_g^0 1
[Fe(CN)_6]^4- t_2g ^6e_g^0 0