If standard reduction potential $(E^{\circ})$ of $(Mg^{2+}_{(aq)} \mid Mg_{(s)})$,$(Ag^{+}_{(aq)} \mid Ag_{(s)})$,$(Zn^{2+}_{(aq)} \mid Zn_{(s)})$ and $(Cu^{2+}_{(aq)} \mid Cu_{(s)})$ are $-2.37 \ V$,$+0.79 \ V$,$-0.76 \ V$ and $+0.34 \ V$ respectively. Which of the following reaction is spontaneous?

• A
  $Zn_{(s)} + Mg^{2+}_{(aq)} \longrightarrow Zn^{2+}_{(aq)} + Mg_{(s)}$
• B
  $2Ag_{(s)} + Zn^{2+}_{(aq)} \longrightarrow 2Ag^{+}_{(aq)} + Zn_{(s)}$
• C
  $Zn_{(s)} + Cu^{2+}_{(aq)} \longrightarrow Zn^{2+}_{(aq)} + Cu_{(s)}$
• D
  $Cu_{(s)} + Mg^{2+}_{(aq)} \longrightarrow Cu^{2+}_{(aq)} + Mg_{(s)}$