The correct option is D (ii)>(i)>(iii)
Groups attached to benzene ring in structures (i) and (iii) shows −M effect, whereas in structure (ii) (−NH2) group shows +M effect.
−M groups decreases the electron density at ortho/para positions on the benzene ring, whereas +M group increases the electron density at ortho/para positions. So, electron density (on benzene ring at ortho and para position) will be the most in (ii).
The order of −M strength for the given groups are :
−CN>−COR
Correct order is :
(ii)>(i)>(iii)
Order of −M effect :
−NO2>−CN>−CHO>−COR>−COOCOR>−COOR>−COOH>−CONH2>−COO−