What is produced when ethanol reacts with sodium metal?

Which of the following is a natural polymer?

An organic compound $A$ of molecular formula $C_{2}H_{4}$ on reduction gives another compound $B$ of molecular formula $C_{2}H_{6}$. $B$ on reaction with chlorine in the presence of sunlight gives $C$ of molecular formula $C_{2}H_{5}Cl$.
$(a)$ Name the compounds $A, B$ and $C$.
$(b)$ Write the chemical equation for the conversion of $A$ to $B$ and name the type of reaction.

What is the name of the aldehyde corresponding to methane?

List two characteristics of covalent compounds.

What are biochemical catalysts called?