During the electrolysis of aqueous $NaCl$ solution, the product formed at the cathode is?

The electrolysis of a certain liquid resulted in the formation of hydrogen at the cathode and chlorine at the anode. The liquid is

$O_2$ gas will be evolved as a product of electrolysis of $:$
$(A)$ an aqueous solution of $AgNO_3$ using silver electrodes.
$(B)$ an aqueous solution of $AgNO_3$ using platinum electrodes.
$(C)$ a dilute solution of $H_2 SO_4$ using platinum electrodes.
$(D)$ a high concentration solution of $H_2 SO_4$ using platinum electrodes.
Choose the correct answer from the options given below $:$

An electrolyte:

Electrolysis of a concentrated aqueous solution of $NaCl$ with graphite electrodes leads to what results at the anode and cathode respectively?

If electrolysis of aqueous $CuSO_4$ solution is carried out using $Cu$ electrodes, the reaction taking place at the anode is: