Given that standard reduction potential of  
 $N{i}^{2+}|Ni=-0.25V$   ;  $C{u}^{2+}|Cu=0.34V$
  $A{g}^{2+}|Ag=0.80V ; Z{n}^{2+}|Zn=-0.76V$
Which of the following reactions under standard condition will not take place in the specific direction?