In the alumino thermite process, $Al$ acts as

$Si$ and $Ge$ used for semiconductors are required to be of high purity and hence purified by

Neutral refractory material used in furnaces is

What is the appropriate process for the extraction of lead from low grade ore (impurity level is high) $(a)$ froth floatation $(b)$ Calcination $(c)$ Roasting $(d)$ Self reduction $(e)$ Electrolytic reduction $(f)$ Smelting $(g)$ Leaching