Which of the following attacks glass ?

Silica on heating to 1600^oc changes to quartz glass quartz is the allotropic form of silica silica(glass) soluble in HF and forms hydrofluorosilicic acid

$$\begin{gathered} {\mathrm{SiO}}_2+4\mathrm{HF}\to {\mathrm{SiF}}_4+2{\mathrm{H}}_2\mathrm{O} \\ 2\mathrm{HF}+{\mathrm{SiF}}_4\to {\mathrm{H}}_2{\mathrm{SiF}}_6 \end{gathered}$$