Correct Answer - C
(A) in `Cr_(2)O_(7)^(2-)` the valenc shell electron configuration of `Cr(VI)` is `3d^(0)`. Thus `Cr(VI)` is diamagnetic but coloured due to the charge transfer spectrum.
(B) In `(NH_(4))_(2)[TiCl_(6)]`, the valence shell electrons configuration of `Ti(IV)` is `3d^(0)` . Thus `Ti(IV)` is diamagnetic and colourless.
(C ) In `VOSO_(4)` , then valence shell electron configuration of `V(IV)` is `3d^(1)`. Thus `V(IV)` is paramagnetic and blue coloured due to d-d transition.
(D) In `K_(3)[Cu(CN)_(4)]`, the valence shell electron configuration of `CU(I)` is `3d^(10)`. Thus `Cu(I)` is diamagnetic and colourless.
