The half-reaction at the cathode in an electrochemical cell is given below. What other half-reaction would most likely occur at the anode to produce a spontaneous reaction? Ni^2(aq)+2e-=Ni(s)

A. Cu(s)=Cu^2+(aq)+2e-
B. Zn(s)=Zn^2+(aq)+2e-
C. Mg^2+(aq)+2e-=Mg(s)
D. Ni(s)=Ni^2+(aq)+2e-