The electronic configuration of $Sc$ $(Z = 21)$ is:

• A
  $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1$
• B
  $1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^2$
• C
  $1s^2 2s^2 2p^6 3s^2 3p^6 4s^0 3d^3$
• D
  $1s^2 2s^2 2p^6 3s^2 3p^2 4s^2 3d^2$