# Silica is eliminated during the process as:

$\begin{array}{1 1}(a)\;Si(Solid)&(b)\;SiO_2(vapour)\\(c)\;SiO_2(solid)&(d)\;Si(vapour)\end{array}$

Silicon(vapour)
$SiO_2+2C\rightarrow Si+2CO$
Hence (d) is the correct answer.