The most basic one is

L.P. on –NH₂ is not involved in resonance.

Basicity means the ability to donate lone pair electrons.
Basicity depends on the negative charge on the nitrogen atom or electron density. With an increase in the -ve charge on the nitrogen atom, the basicity of the amines increases. Basicity depends on charge density. Resonance and inductive effects decrease the basicity of an amine. Since in resonance the electron density is not in a fix position.