Which of the following statements are correct?
a) The electrolysis of aqueous NaCl produces hydrogen gas at the cathode and chlorine gas at the anode .
b) The electrolysis of a CuSO4 solution using Pt electrodes causes the liberation of O2 at the anode and the deposition of copper at the cathode .
c) Oxygen and hydrogen are produced at the anode and cathode during the electrolysis of dilute aqueous solution of H2SO4 .
d) All electrolytic reactions are redox reactions .
Which of the following substance gets liberated at the anode during the electrolysis of aqueous NaCl?