Which alkyne yields butanoic acid $(CH_3CH_2CH_2CO_2H)$ as the only organic product on treatment with ozone followed by the hydrolysis?

The reaction of $2-$butyne with $HgSO_4/H_2SO_4$ yields.............

The number of possible structural alkynes with molecular formula $C_5H_8$ is

In which of the following,the bond length between the hybridized carbon atom and the other carbon atom is minimum?

$But-2-yne$ and hydrogen (one mole each) are separately treated with $(i)$ $Pd / C$ and $(ii)$ $Na / \text{liq. } NH_3$ to give the products $X$ and $Y$ respectively. Identify the incorrect statements.
$A$. $X$ and $Y$ are stereoisomers.
$B$. Dipole moment of $X$ is zero.
$C$. Boiling point of $X$ is higher than $Y$.
$D$. $X$ and $Y$ react with $O_3 / Zn + H_2O$ to give different products.
Choose the correct answer from the options given below:

Which of the following compounds contains an acidic hydrogen?