The correct statement(s) about the following molecule is or are

The nitrogen Atom involved in the bond ‘b’ is pushed out of the plane by the two ortho methyl substituents. Therefore, the lone pair on this nitrogen does not get localised much in benzene ring. This is called steric inhibition to resonance.
So, bond ‘b’ has less double bond character than bond ‘a’.
Hence, (A), (C) and (D) are correct.