Identify the structure of $M$ based on the following reaction scheme:

Identify the structure of the final product $(D)$ in the following sequence of reactions:
$Ph-CO-CH_3$ $\xrightarrow{PCl_5, \Delta} A$ $\xrightarrow{3 \text{ eq. } NaNH_2/NH_3} B$ $\xrightarrow{\text{Acidify}} C$ $\xrightarrow{1. B_2H_6, 2. H_2O_2/OH^-} D$
Total number of $sp^2$ hybridised carbon atoms in product $D$ is:

But$-1-$yne on reaction with dil. $H_2SO_4$ in the presence of $Hg^{2+}$ ions at $333 \ K$ gives:

When $1,2-$dibromopropane is treated with $X$ moles of $NaNH_2$,the resulting compound reacts with ethyl bromide to form pentyne. What is the value of $X$?

What product is obtained when acetylene is passed through dilute sulfuric acid containing $Hg^{2+}$ ions?

The product $(B)$ is: