In Hoffmann bromamide degradation, one of the important steps is the migration of:

The major product of the following reaction is:

The Hinsberg test of a ${\mathrm{C}}_5{\mathrm{H}}_{14}{\mathrm{N}}_2$ compound produces a solid that is insoluble in $10\%$ aq. $\mathrm{NaOH}.$ This solid derivative dissolves in $10\%$ aq. ${\mathrm{H}}_2{\mathrm{SO}}_4.$

 Which of the following would best fit these facts?

The final product $\left(\mathrm{B}\right)$ is:

Guanidine, ${\left({\mathrm{NH}}_2\right)}_2\mathrm{C}=\mathrm{NH},$ is said to be the strongest nitrogen containing organic base because:

[B] in given reaction is

 $\left[\mathrm{A}\right] \stackrel{\left[\mathrm{B}\right]/\mathrm{Conc}.{\mathrm{H}}_2{\mathrm{SO}}_4}{\to }\left[\mathrm{C}\right] \underset{5°\mathrm{C}}{\overset{{\mathrm{NaNO}}_2,\mathrm{HCl}}{\to }}\left[\mathrm{D}\right] \stackrel{\mathrm{CuCl}}{\to }\mathrm{p}-$ Nitrochlorobenzene