The isomer of ${\mathrm{C}}_6{\mathrm{H}}_{14}$, which will give maximum number of monochloroderivative is

Treatment of ammonia with excess of ethyl chloride will yield 

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

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