What is obtained by the reaction of calcium carbide with heavy water?

The number and type of bonds between two carbon atoms in $CaC_2$ are

In the following reaction,compound $A$ is formed,which reacts with $B$ to give product $C$. Identify $A$ and $B$.

Formation of ethylene from acetylene is an example of

One mole of $1,2$-dibromopropane on treatment with $X$ moles of $NaNH_2$ followed by treatment with ethyl bromide gave a pentyne. The value of $X$ is

In the reaction $CH_3-CH_2-C \equiv CH + HCl \to B \xrightarrow{HI} C$,what is the product $C$?