Which of the following electronic configurations in the outermost shell is characteristic of alkali metals?

• A
  $(n - 1)s^2p^6, ns^2p^1$
• B
  $(n - 1)s^2p^6d^{10}, ns^1$
• C
  $(n - 1)s^2p^6, ns^1$
• D
  $ns^2p^6d^1$