Which of the following pair of metals are extracted by self-reduction from their main ores but do not evolve $H_2$ gas with dilute $H_2SO_4$?

Consider the following reactions of metallurgy:
Ore '$X$' $\xrightarrow{\text{Roasting}}$ '$Y$' + $SO_2$ $\uparrow$
Ore '$Z$' $\xrightarrow{\text{Calcination}}$ '$Y$' + $CO_2$ $\uparrow$
'$Y$' + $C$ $\xrightarrow{1673 \ K}$ '$A$' (vapour) + '$B$' $(g)$
where '$A$' and '$B$' are respectively:

In the Goldschmidt thermite process,which substance acts as the reducing agent?

Which statement is incorrect regarding the Hall-Heroult process for the metallurgy of aluminium?
$1$. Use of $Na_3AlF_6$ lowers the melting point of $Al_2O_3$.
$2$. Steel vessel with a lining of carbon acts as the cathode.
$3$. Graphite is used as the anode.
$4$. Carbon dioxide gas is generated at the cathode.

The cyanide process is used in the extraction of:

What does the slag obtained during the extraction of copper mainly consist of?