$A$ metal which is refined by poling is

What is the composition of the anode mud in the electrolytic refining of silver?

Electric refining is used for refining of

Poling process is used for

Choose the correct option for vapor phase refining.
$A :$ The metal should form a volatile compound with an appropriate reagent.
$R :$ The volatile compound obtained should be easily decomposable.

Match the elements in Column-$I$ with methods of purification in Column-$II$.

Column-$I$	Column-$II$
$(a)$ Boron	$(i)$ Van Arkel method
$(b)$ Tin	$(ii)$ Mond's process
$(c)$ Zirconium	$(iii)$ Liquation
$(d)$ Nickel	$(iv)$ Zone refining