Given the following half-reactions, determine which overall reaction is spontaneous and calculate the cell potential: Mg2+(aq) + 2 e Mg(s), E = 2.37 V Ni2+(aq) + 2 e Ni(s), E = 0.25 V (A) Mg2+(aq) + Ni(s) Mg(s) + Ni2+(aq), E = +2.12 V (B) Mg2+(aq) + Ni2+(aq) Mg(s) + Ni(s), E = 2.12 V (C) Mg(s) + Ni2+(aq) Mg2+(aq) + Ni(s), E = +2.12 V (D) Mg2+(aq) + Ni(s) Mg(s) + Ni2+(aq), E = 2.62 V