The longest $\mathrm{C}-\mathrm{N}$ bond length in the given compound is:

Select the correct order of heat of hydrogenation?

 $\left(\mathrm{I}\right)$ 

$\left(\mathrm{II}\right)$ 

$\left(\mathrm{III}\right)$ 

$\left(\mathrm{IV}\right)$ 

In this molecules, $\mathrm{\pi }$-electron density is more on:

The correct order of electron density in the aromatic ring of the following compounds is:​​​​​​