Which flux is used to remove $SiO_2$ impurity?

Which of the following is incorrect on the basis of the Ellingham diagram for carbon?

Suggest a condition under which magnesium could reduce alumina. The two equations are:
$(a)$ $\frac{4}{3} Al + O_2 \rightarrow \frac{2}{3} Al_2O_3$
$(b)$ $2 Mg + O_2 \rightarrow 2 MgO$

Extraction of silver is achieved by initial complexation of the ore (argentite) with $X$ followed by reduction with $Y$. $X$ and $Y$,respectively are

In a blast furnace,iron oxide is reduced by:

In the extraction of copper from copper pyrites,iron is removed as