Of the following acids, the one which has the capability to form complex compounds and also possesses both oxidizing and reducing properties is:

The basic building unit of all silicates is

Match the following:

List-$I$ (Compound)	List-$II$ (Use)
$A$. Kieselghur	$I$. Chromatographic material
$B$. Silica gel	$II$. Softening of hard water
$C$. $ZSM-5$	$III$. Filtration plants
$D$. Hydrated zeolites	$IV$. To convert alcohol directly into gasoline

Assertion : $SiF_6^{2-}$ is known but $SiCl_6^{2-}$ is not.
Reason : Size of fluorine is small and its lone pair of electrons interacts with $d-$orbitals of $Si$ strongly.

Evaluate the following statements related to group $14$ elements for their correctness.
$(A)$ Covalent radius decreases down the group from $C$ to $Pb$ in a regular manner.
$(B)$ Electronegativity decreases from $C$ to $Pb$ down the group gradually.
$(C)$ Maximum covalence of $C$ is $4$ whereas other elements can expand their covalence due to presence of $d$ orbitals.
$(D)$ Heavier elements do not form $p\pi-p\pi$ bonds.
$(E)$ Carbon can exhibit negative oxidation states.
Choose the correct answer from the options given below:

What are allotropes? Sketch the structure of two allotropes of carbon namely diamond and graphite. What is the impact of structure on physical properties of two allotropes?