• Here the -NH2 (amine) group is attached directly to the benzene ring. Hence, the unshared electron pair on the nitrogen atom(i.e. lone pair) will be engaged in conjugation (forming resonating structures) with the benzene ring and thus it becomes almost unavailable for protonation by the acids.

• Other 3 options (ii) (iii) and (iv) CH₃NH₂ the above scenario is not possible and therefore they are better and stronger Brönsted bases ; (iv) being the strongest.