The correct option is "Cd²⁺".
When an element achieves pseudo noble gas configuration it means it has 18 electrons in the highest energy level instead of 8.
The electronic configuration of cadmium is:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d1¹⁰
and the electron configuration of Cd²⁺ is1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 4d¹⁰