Predict the product $(A)$ of the following reaction:

$A$ hydrocarbon $C_5H_8$ consumes two moles of hydrogen. On ozonolysis,it produces $2-$oxopropanal and methanal. The hydrocarbon is:

$2, 4$-hexadiyne $(CH_3-C\equiv C-C\equiv C-CH_3)$ is allowed to react with $Li$ in $NH_3$ $(liq)$. The product obtained is treated with $1$ equivalent of $Cl_2$ in $CCl_4$. Which of the following constitutional isomers are possible products?

Which of the following reactions results in the formation of a pair of diastereomers?

The number of isomeric tetraenes ($NOT$ containing $sp$-hybridized carbon atoms) that can be formed from the following reaction sequence is.....

In the reaction,
$C_5H_6 + CH_3COCH_3 \xrightarrow{EtONa/EtOH, \text{heat}} X$,
the product $(X)$ is