A. Zn (s) + Cd2+ (aq) → Zn2+ (aq) + Cd (s);
E° Cd2+ / Cd= - 0.404V, E° Zn2+ / Zn=-0.763V
B. Cu (s) + ZnSO4 (aq)→ CuSO4 (aq) + Zn (s);
E° Cu2+ / Cu = 0.34V, E° Zn2+ / Zn = -0.76V
C. 2Ag (s) + 2H+ (aq)→ 2Ag+ (aq) + H2 (g);
E° Ag+/Ag= 0.80V
D. 3Sn2+ (aq) + 2Fe(s)→2Fe3+ (aq) + 3Sn(s);
E°Fe3+/Fe= 0.036V, E° Sn2+ / Sn = -0.140V