Tetrahalides of group $14$ elements (except that of carbon) act as

Which of the following properties correctly explain $SiO_2$?

Provide information about silicon compounds (silicates).

Consider the following statements:
$I$. In diamond,each carbon atom is $sp^3$-hybridised.
$II$. Graphite has planar hexagonal layers of carbon atoms.
$III$. Silicones being surrounded by non-polar alkyl groups are water repelling in nature.
$IV$. The order of catenation in group $14$ elements is $Si > C > Sn > Ge > Pb$.
The correct statements are:

Gas $A$ is bubbled through slaked lime when a white precipitate is formed. On prolonged bubbling,the precipitate is dissolved. On heating the resultant solution,the white precipitate reappears with the evolution of gas $B$. The gases $A$ and $B$ respectively are

Explain the following reactions:
$(a)$ Silicon is heated with methyl chloride at high temperature in the presence of copper;
$(b)$ Silicon dioxide is treated with hydrogen fluoride;
$(c)$ $CO$ is heated with $ZnO$;
$(d)$ Hydrated alumina is treated with aqueous $NaOH$ solution.