In Van Arkel method, if $I_2$ is introduced at $1800 \mathrm{K}$ over impure zirconium metal, the product will be :

The following reaction is obtained,

$\begin{array}{l}\mathrm{Zr}\text{ (impure) }+2{\mathrm{I}}_2\stackrel{<1800\mathrm{K}}{\to }{\mathrm{ZrI}}_4\\ {\mathrm{ZrI}}_4\stackrel{>1800\mathrm{K}}{\to }\mathrm{Zr}\left(\text{ pure }\right)+2{\mathrm{I}}_2\end{array}$

A practical interaction between Zr and ${\mathrm{I}}_2$ at temperatures beyond 1800K is possible. As a result, option (d) is right.