Which of the following processes is non-spontaneous?

• A
  $F_{(g)} + Cl_{(g)}^{+} \to F_{(g)}^{+} + Cl_{(g)}$
• B
  $O_{(g)}^{-} + S_{(g)} \to O_{(g)} + S_{(g)}^{-}$
• C
  $Be_{(g)}^{-} + B_{(g)} \to Be_{(g)} + B_{(g)}^{-}$
• D
  $N_{(g)} + O_{(g)}^{+} \to N_{(g)}^{+} + O_{(g)}$