Correct Answer - C
`Fe^(+3)` is isoelectronic with `Mn^(+2)` as both have same number of `e^-` and electronic configuration
`Fe^(+3) (3d^5 4s^0) " " Mn^(+2) (3d^5 4s^0)`
Electronic configuration of other ions are `Cu^(+2)(3d^9 4s^0) " "Co^(+2)(3d^7 4s^0) " " Ni^(+2) (3d^8 4s^0)`
