$CH_3-C \equiv C-CH_3$ $\xrightarrow[(1) \ O_3]{(2) \ H_2O} X$ $\xrightarrow[\Delta]{NaOH + CaO} Y$; $Y$ is

The best sequence of reactions to prepare $2$-heptanone is

$2-$butyne is reduced to $trans-but-2-ene$ using:

By heating a mixture of $CHCl_3$ with silver powder,the compound formed is

Given below are two statements:
Statement $I$: One mole of propyne reacts with excess of sodium to liberate half a mole of $H_2$ gas.
Statement $II$: Four $g$ of propyne reacts with $NaNH_2$ to liberate $NH_3$ gas which occupies $224 \ mL$ at $STP$.
In the light of the above statements,choose the most appropriate answer from the options given below:

$A$ gas decolourises bromine in $CCl_4$ and forms a precipitate with ammoniacal silver nitrate. The gas is