Which of the following compounds contains an acidic hydrogen?

When acetylene is passed through a solution of dilute sulfuric acid containing mercuric sulfate,the number of $\pi$ bonds in the final product obtained is.........

$A$ $\xrightarrow[1\% \ HgSO_4]{20\% \ H_2SO_4} B$ $\xrightarrow{I_2 + NaOH} C + C_6H_5COONa$. The reactant $A$ is

Identify $Z$ in the following sequence:
$C_3H_7OH$ $\xrightarrow{H_2SO_4} X$ $\xrightarrow{Br_2} Y$ $\xrightarrow{KOH} Z$

What is formed when phenylacetylene reacts with dilute $HgSO_4$ in the presence of $H_2SO_4$?

$Ph-C \equiv CH \xrightarrow[MeOH]{MeO^{-}}$ The major product of the reaction is: