Which of the following elements does not form a monoxide?

Assertion $(A)$: Graphite is used as a dry lubricant in machines which run at high temperatures.
Reason $(R)$: The layers of graphite slip one over the other when pressure is applied.
The correct option among the following is:

Which allotrope of carbon is isomorphous with crystalline silicon?

The basic building unit of all silicates is

$A$ compound $A$ is used in paints instead of salts of lead. Compound $A$ is obtained when a white compound $B$ is strongly heated. The compound $B$ is insoluble in water but dissolves in $NaOH$ solution,forming a solution of compound $C$. The compound $A$ on heating with coke gives a volatile metal $D$ and a gas $E$ which burns with a blue flame. Identify the possible species $D$ and $C$ respectively.

Which gas is used in aerated water?