$$ \text { Observe the following reactions } $$

The correct order of reactivity of $X, Y, Z$ towards $\mathrm{S}_{\mathrm{N}} 1$ reaction is

Identify the compound $(Z)$ in the following reaction sequence

Identify the product ' $Y$ ' in the given sequence of reactions

The empirical formula of the compound ' $D$ ' formed in the given reaction sequence is

$$ \mathrm{C}_2 \mathrm{H}_4 \xrightarrow{\mathrm{Br}_2 / \mathrm{CCl}_4} A \xrightarrow[\text { (ii) } \mathrm{NaNH}_2]{\text { (i) } \mathrm{Alc} \cdot \mathrm{KOH}} B \xrightarrow[\text { polymerisation }]{\text { Cyclic }} C \xrightarrow[\text { DryAlCla }{ }_3 \text {, dark.cold }]{\mathrm{Cl}_2 \text { (excess) }} $$