State the balanced, net-ionic equations for the cell reactions for the subsequent half-cell combinations at standard conditions. Be sure to consider direction of spontaneity.
A. Cu/Cu2+, Ag/Ag+
B. Ag/Ag+, Zn/Zn2+
C. Mg/Mg2+, Pb/Pb2+
D. Ni/Ni2+, Mg/Mg2+
E. Cu/Cu2+, Pb/Pb2+