Match list-I with list-II :

List-I		List-II
(a)   Mercury	(i)	Vapour phase refining
(b)   Copper	(ii)	Distillation refining
(c)   Silicon	(iii)	Electrolytic refining
(d)   Nickel	(iv)	Zone refining

Choose the most appropriate answer from the option given below:

Mercury is a liquid metal with a low boiling point, so it is purified by distillation refining, giving $$a \to (ii)$$.

Copper is refined industrially by electrolytic refining, where impure copper is the anode and pure copper deposits on the cathode in a $$\text{CuSO}_4$$ solution, giving $$b \to (iii)$$.

Silicon is a semiconductor that requires extremely high purity. It is purified by zone refining, where a narrow molten zone is moved along a rod so that impurities concentrate at one end, giving $$c \to (iv)$$.

Nickel is purified by the Mond process, a vapour phase refining method. Impure nickel reacts with $$\text{CO}$$ at about 330 K to form volatile $$\text{Ni(CO)}_4$$, which is then decomposed at higher temperature (450 K) to deposit pure nickel, giving $$d \to (i)$$.

The correct matching is $$a$$-(ii), $$b$$-(iii), $$c$$-(iv), $$d$$-(i), which corresponds to option (3).