The reagent used to convert an alkyne to an alkene is:

$A$ mixture of methane,ethylene,and acetylene gases is passed through a Wolf's bottle containing ammoniacal cuprous chloride. The gas coming out is

In the reaction
$HC \equiv CH \xrightarrow[(ii) CH_3CH_2Br]{(i) NaNH_2 / liq. NH_3} X$
$\xrightarrow[(ii) CH_3CH_2Br]{(i) NaNH_2 / liq. NH_3} Y$
$X$ and $Y$ are

Which of the following compounds is capable of reacting with ammoniacal $AgNO_3$ solution?

The general formula of an alkyne is:

The two carbon atoms in acetylene are