A cell is built using two electrodes: What reaction occurs at the cathode?

Al3+ + 3e —> Al E° = -1.66V

Cu2+ + 2e —> Cu E° = +0.34V

ACu —> Cu2+ + 2e-

BCu2+ + 2e- —> Cu

CAl3+ + 3e- —> Al

DAl —> Al3+ + 3e-