During the electrolysis of copper sulphate aqueous solution using copper electrode, the reaction taking place at the cathode is :

Question

$$\begin {array} {1 1}(a)\;Cu \to Cu^{2+} _{(aq)}+2e^{-} \\ (b)\;Cu^{2+}_{(aq)}+2e^{-} \to Cu_{(s)} \\ (c)\;H^{+}_{(aq)}+e^{-} \to \frac {1}{2} H_{2(g)} \\ (d)\; SO_{4(aq)}^{2-} \to SO_{3(g)}+\frac{1}{2} O_{2(g)}+2e^{-}\end {array}$$