The correct option is D all of the above
Answer is D.
Electrolysis has wide applications in industries. Some of the important applications are, as follows,
(i) Production of hydrogen by electrolysis of water.
(ii) Manufacture of heavy water.
(iii) The metals like K, Mg, Al, etc., are obtained by electrolysis of fused electrolytes.
(iv) Non-metals like hydrogen, fluorine, chlorine are obtained by electrolysis.
(v) In this method pure metal is deposited at cathode from a solution containing the metal ions, etc.
(vi) Compounds like NaOH, KOH, white lead, etc. are synthesised by electrosynthesis method.
(vii) Electroplating: The process of coating an inferior metal with a superior metal by electrolysis is known as electroplating.
Hence, the options A, B and C are correct.