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

Supply the structure of bracketed compound in the following conversion.

Supply the structure of bracketed compound in the following conversion.

Supply the structure of bracketed compound in the following conversion.

Supply the structure of bracketed compound in  the following conversion.

  $\underset{{\mathrm{H}}_2{\mathrm{SO}}_4}{\overset{{\mathrm{HNO}}_3}{\to }}\left[\mathrm{A}\right]$