$CH_3-CH_2-C \equiv CH \xrightarrow{R, H_2O} \text{Butanone}$. $R$ is:

$CH_3-C \equiv C-O-CH_3 \xrightarrow{dil. \ H_2SO_4, HgSO_4} \text{major product}$

Which of the following is the most acidic substance?

In the given reaction,
$Ph-C \equiv C-CH_3 \xrightarrow{H^{+}/Hg^{2+}} A$
the product $A$ is

Which of the following has the shortest $C - C$ bond length?

$A$ hydrocarbon $X$ with molecular formula $C_4H_6$ decolourises bromine water and forms a white precipitate in ethanolic $AgNO_3$ solution. Treatment of $X$ with $HgCl_2$ in aqueous $H_2SO_4$ produces a compound,which gives a yellow precipitate when treated with $I_2$ and $NaOH$. The structure of $X$ is