The correct option for the first ionisation enthalpy (in $kJ \ mol^{-1}$) of $Li$,$Na$,$K$ and $Cs$ respectively is

• A
  $496, 520, 419, 374$
• B
  $374, 419, 496, 520$
• C
  $520, 496, 419, 374$
• D
  $374, 419, 520, 496$