(i) In CH₃NH₂ the +I effect of −CH₃ group makes lone pair of electrons on N− atom more available for donation. On the other hand in C₆H₅NH₂, the resonance effect causes delocalisation of lone pair of electrons over benzene ring and makes it less available for donation. Hence, CH₃NH₂ is more basic than C₆H₅NH₂

(ii) CH₃NH₂ is more basic than NH₃. The −CH₃ group due to its +I effect pushes electron towards nitrogen and this makes the unshared electron pair more available for sharing with the proton of the acid.

(iii) As −CH₃ group is electron releasing by +I effect ; hence p-toludine is more basic than aniline.