The correct electronic configuration of $Fe^{3+}$ $[Z=26]$ is:

• A
  $1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^5$
• B
  $1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^3, 4s^2$
• C
  $1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^6, 4s^2$
• D
  $1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^5, 4s^1$