Which are the various forms of silica?

The main reason that $SiCl_{4}$ is easily hydrolysed as compared to $CCl_{4}$ is that

Among the following options, the element with the highest density and lowest boiling point is

If the starting material for the manufacture of silicones is $RSiCl_3$,write the structure of the product formed.

Which one of the following oxides is expected to exhibit paramagnetic behaviour?

Choose the correct statements about allotropes of carbon:
$I$. Graphite has a layered structure.
$II$. Buckminsterfullerene is not aromatic in nature.
$III$. The distance between two adjacent layers in graphite is $340 \ pm$.
$IV$. The hybridization of carbons in graphite and Buckminsterfullerene is the same $(sp^2)$.