The extraction of which of the following metals involves bessemerisation?

The metal which is extracted by oxidation and subsequent reduction from its ore is:

During the electrolytic reduction of alumina,two auxiliary electrolytes $X$ and $Y$ are added to increase the electrical conductance and lower the melting point of the mixture. $X$ and $Y$ are:

Smelting is carried out in a ...... .

Axles are made by heating rods of iron embedded in charcoal powder. The process is known as

Gold is extracted by a hydrometallurgical process based on its property: