Which of the following orders is true regarding the basic nature of ${\mathrm{NH}}_2$ group?

Aniline:

The lone pair of electrons present on nitrogen of aniline will be free to donate to protons or elctrophiles to form ammonium ion

o-Toluidine :

In lone pair of electrons present on nitrogen of aniline will be free to donate to protons or elctrophiles to form ammonium ion. After formation of ammonium ion the o-Toluidinium ion is highly unstable due to steric hindrance from methyl group at ortho position. Therfore equilibrium shifted to more stable o-Toluidine side. Hence it is less basic than aniline 

o-Nitroaniline :

It is least basic among all due to –I effect of nito group at ortho position. Nito group at ortho position withdraw electrons towards itself and makes benzene nucleus of aniline electron deficient. This electron deficient nucleus withdraw electrons from nitrogen. So lone pair of electrons present on nitrogen in o-Nitroaniline are not free to donate to protons or electrophiles