Identify the alkyne formed by the reaction of calcium carbide with water.

The reaction of $2-$pentyne with dilute $H_2SO_4$ and $HgSO_4$ yields...............

When calcium carbide is added to water,the gas that is evolved is

An inorganic metal oxide $(A)$ heated with carbon gives compound $(B)$,which on reaction with water gives ethyne. What are the compounds $(A)$ and $(B)$?

Identify $A$ in the following reaction.
$A$ $\xrightarrow{\text{Lithium amide}} \text{Ethynyl lithium}$ $\xrightarrow{\text{Bromoethane}} \text{but-}1\text{-yne}$

Which of the following has acidic hydrogen?