Which metal is most difficult to be extracted from its oxide?

Copper sulphate is commercially made from copper scraps by:

Which of the following has maximum iron content?

Aluminium is used as a reducing agent in the reduction of

Statement $I :$ Leaching of gold with cyanide ion in absence of air $/$ $O_2$ leads to cyano complex of $Au(III)$.
Statement $II :$ Zinc is oxidized during the displacement reaction carried out for gold extraction.
In the light of the above statements,choose the correct answer from the options given below.

After partial roasting,the sulphide of copper is reduced by