In which of the following,the bond length between the hybridized carbon atom and the other carbon atom is minimum?

The product $Z$ of the following reaction is
$CH_3-C \equiv CH \xrightarrow{2 HBr} Z$

Which one is the correct order of acidity?

In which of the following molecules,$2$ $\pi$ bonds are present?

An unknown compound $X$ is an unsaturated hydrocarbon. It reacts with $HgSO_4$ and $H_2SO_4$ to give compound $(B)$. Compound $(B)$ on oxidation gives compound $(C)$. Compound $(C)$ on reaction with $NaOH$ and soda lime gives methane. Identify $A$ (which is $X$),$B$,and $C$ by providing the chemical reactions.

Which hydrocarbon reacts with sodium in liquid ammonia?