How many corners of $SiO_4$ units are shared in the formation of three dimensional silicates?

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

Which of the following elements does not form a monoxide?

The formation of $Al_2O_3$ involves the evolution of a large quantity of heat,which makes its use in:

The $INCORRECT$ statement regarding the structure of $C_{60}$ is :

Superphosphate of lime contains