It takes 2.9 x 10$ coulombs of electricity to deposit 1.0 mol of a metal X at the cathode during electrolysis of a molten compound of X. The equation that

best represents the change occurring at the cathode is \text { A. } X^{+}(1)+e^{-} \rightarrow X(s) \text { B. } X^{2+}(1)+2 e^{-} \rightarrow X(s) \text { C. } X^{3+}(1)+3 e^{-} \rightarrow X(s) \text { D. } X^{4+}(l)+4 e^{-} \rightarrow X(s)