The correct order of ${\mathrm{K}}_{\mathrm{b}}$ is

(i)

(ii)

(iii) ${\mathrm{CH}}_3{\mathrm{CH}}_2-{\mathrm{NH}}_2$

(iv) ${\mathrm{H}}_3\mathrm{C}-\underset{\stackrel{\left|\right|}{\mathrm{O}}}{\mathrm{C}}-{\mathrm{NH}}_2$

In pyrrole

The electron density is maximum on:

The correct increasing order of basic strength for the following compounds is:

Arrange the following in the correct decreasing order of ${\mathrm{pK}}_{\mathrm{b}}$:

Arrange the following in the decreasing order of basic strength

(I)	(II)	(III)	(IV)

What is $\mathrm{B}$?

$\mathrm{B}$ is :- 

The number of structural isomers possible from the molecular formula ${\mathrm{C}}_3{\mathrm{H}}_9\mathrm{N}$ is ______.