Consider the following route of reactions $R_2SiCl_2 + H_2O \to (A) \xrightarrow{\text{Polymerisation}} (B)$. Compound $(B)$ in the above reaction is:

Identify the element whose monoxide and dioxide are acidic in nature.

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

Assertion $(A)$: Graphite is used as a dry lubricant in machines which run at high temperatures.
Reason $(R)$: The layers of graphite slip one over the other when pressure is applied.
The correct option among the following is:

The composition of common glass is:

$A$ tetravalent element forms monoxide and dioxide with oxygen. When air is passed over the heated element $(1273 \ K)$,producer gas is obtained. The monoxide of the element is a powerful reducing agent and reduces ferric oxide to iron. Identify the element and write the formulas of its monoxide and dioxide. Write chemical equations for the formation of producer gas and the reduction of ferric oxide with the monoxide.