Give the anode reaction for an electrode of any metal $M \,|\, M^{n+}$.

• A
  $M(s) \rightarrow M^{n+}(aq) + ne^-$
• B
  $M^{n+}(aq) + ne^- \rightarrow M(s)$
• C
  $M(s) + ne^- \rightarrow M^{n+}(aq)$
• D
  $M^{n+}(aq) \rightarrow M(s) + ne^-$