Which of the following statements are correct?
$i$. The basic structural unit of silicates is $SiO_4^{4-}$
$ii$. Silicones are biocompatible
$iii$. Producer gas contains $CO$ and $N_2$
The correct option is

Match the species given in Column-$I$ with the properties mentioned in Column-$II$.

Column-$I$	Column-$II$
$A$. $BF_4^-$	$1$. Oxidation state of central atom is $+4$
$B$. $AlCl_3$	$2$. Strong oxidizing agent
$C$. $SnO$	$3$. Lewis acid
$D$. $PbO_2$	$4$. Can be further oxidized
	$5$. Tetrahedral shape

In which of the following commercial processes is a catalyst not used?

It is observed that $Pb^{2+}$ is more stable than $Pb^{4+}$, while $Sn^{2+}$ is less stable than $Sn^{4+}$. Consider the following reactions:
$PbO_{2} + Pb \rightarrow 2PbO; \Delta_{r}G^{\circ} (1)$
$SnO_{2} + Sn \rightarrow 2SnO; \Delta_{r}G^{\circ} (2)$
Identify the correct set from the following.

Concentrated hydrochloric acid when kept in open air sometimes produces a cloud of white fumes. The explanation for it is that

With respect to graphite and diamond,which of the statement$(s)$ given below is (are) correct?
$(A)$ Graphite is harder than diamond.
$(B)$ Graphite has higher electrical conductivity than diamond.
$(C)$ Graphite has higher thermal conductivity than diamond.
$(D)$ Graphite has higher $C-C$ bond order than diamond.