The correct statement(s) related to the metal extraction processes is(are):
A mixture of \( \text{PbS} \) and \( \text{PbO} \) undergoes self-reduction to produce \( \text{Pb} \) and \( \text{SO}_2 \)
In the extraction process of copper from copper pyrites, silica is added to produce copper silicate
Partial oxidation of sulphide ore of copper by roasting, followed by self-reduction produces blister copper
In cyanide process, zinc powder is utilized to precipitate gold from \( \text{Na[Au(CN)}_2\text{]} \)