Correct Answer - D
The no. of unpaired electrons in all the ions are listed.
In `CrO_(4)^(2-),Cr^(+6)(n=0)` diamagnetic
In `Cr_(2)O_(7)^(2-),Cr^(+6)(n=0)` diamagnetic
In `MnO_(4)^(-),Mn^(+7)(n=0)` diamagnetic
In `MnO_(4)^(2-),Mn^(+6)(n=1)` diamagnetic
Thus `MnO_(4)^(2-)` ion is paramagnetic and also exhibits d-d transition.