The reaction of ethene with oxygen in the presence of a silver catalyst gives ....................

The conversion of $2,3-$dibromobutane to $2-$butene with $Zn$ is

The major product of the following reaction is:

$A$ single compound of the structure $CH_3-CO-CH_2-CH_2-CH_2-CHO$ is obtainable from the ozonolysis of which of the following cyclic compounds?

The correct statement about $C$ and $D$ is:
$CH_3-C \equiv C-CH_3$ $\xrightarrow{H_2/Pd-BaSO_4} A$ $\xrightarrow{Br_2/CCl_4} C$
$CH_3-C \equiv C-CH_3$ $\xrightarrow{Na/Liq. NH_3} B$ $\xrightarrow{Br_2/H_2O} D$

If $HCl$ is added to the following substance,what is formed?