Which of the following is most reactive towards electrophilic aromatic substitution for halogen?

Treatment of ammonia with excess of ethyl chloride will yield 

Identify $\mathrm{Z}$ in the following sequence

${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{Br}\stackrel{\mathrm{KCN}}{⟶}\overline{)\mathrm{X}}\underset{\mathrm{\Delta }}{\stackrel{\mathrm{dil}. \mathrm{HCl}}{\to }}\overline{)\mathrm{Z}}$

For the reaction, 

${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}+\mathrm{HX}\stackrel{{\mathrm{ZnX}}_2}{⟶}{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{X},$ the order of reactivity is: