Polyphosphates are used as water softening agents because they .......

The element that shows greater ability to form $p\pi - p\pi$ multiple bonds is

$(BN)_n$ exists in

Which of the following oxides reacts with both $HCl$ and $NaOH$?

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:

Producer gas is a mixture of