Which of the following is the pyrosilicate ion?

$A$ 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.

Identify $B$ in the following reaction:
$H_4SiO_4$ $\xrightarrow[{-H_2O}]{1000^{\circ}C} A$ $\xrightarrow[\Delta]{Carbon} B + CO$

Which of the following is an incorrect statement?

Sulphur is most soluble in

Assertion $(A): [SiF_6]^{2-}$ is formed but $[SiCl_6]^{2-}$ is not.
Reason $(R):$ Electronegativity $(EN)$ of $F$ is higher than $EN$ of $Cl$.