Atomic structure — practice question

What electronic configuration does an isolated $\text{Ni}^{2+}$ ion have?

• A$1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,3d^6\,4s^2$
• B$1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,3d^8\,4s^2$
• C$1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,3d^{10}\,4s^2$
• D$1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,3d^8$