An example of a neutral oxide is

$CO_2$ and $N_2$ do not support combustion. However,$CO_2$ is preferred over $N_2$ for extinguishing fires because $CO_2$ .......

Assertion $(A)$: The maximum covalency of $Si$ and $Ge$ is $6$ but that of carbon is $4$.
Reason $(R)$: Due to the presence of $d$-orbitals in $Si$ and $Ge$,both these elements can undergo $sp^3d^2$ hybridisation and covalency of $6$ is possible. Carbon has no $d$-orbitals in it and hence its covalency is $4$.
The correct answer is:

Dry ice is

When graphite is subjected to an electric arc in the presence of an inert atmosphere,it gives:

At high temperature,nitrogen combines with calcium carbide $(CaC_2)$ to give: