Explanation

(c)
In Fe extraction limestone is used for the formation of slag. The central zone where the temperature varies from 800-1000${^\circ}$C; the lime-stone present in the charge decomposes into calcium oxide and carbon dioxide.
${CaO}_{3}\ \overset{1000{^\circ}C}{\rightarrow}CaO + {CO}_{2}$
The calcium oxide acts as flux and combines with silica present as an impurity to form a fusible slag of ${CaSiO}_{3}$.
$CaO + {SiO}_{2} \longrightarrow {CaSiO}_{3}\$