Explanation

(d)
Copper metallurgy involves bessmerization. In Bessemer convertor, the impurities of ferric oxide forms slag with silica and copper oxide is reduced to give blister copper.
$FeO + {SiO}_{2}\ \longrightarrow {FeSiO}_{3}$
slag
${Cu}_{2}S + 2{Cu}_{2}O\ \longrightarrow 6Cu + {SO}_{2}$