Which of the following decolorizes $Br_2$ water solution?

$CH \equiv CH$ $\xrightarrow{O_3/NaOH} X$ $\xrightarrow{Zn/CH_3COOH} Y$. '$Y$' is:

Acetylene is obtained by the electrolysis of

Which one of the following carbonyl compounds cannot be prepared by addition of water on an alkyne in the presence of $HgSO_4$ and $H_2SO_4$?

Identify the compound $(Z)$ in the following reaction sequence: $CH_3-CH(Br)-CH_2Br$ $\xrightarrow{alc. KOH, \Delta}$ $\xrightarrow{NaNH_2}$ $\xrightarrow{H_2O, Hg^{2+}, H^+} (Z)$

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.........