Hi! I wanted to be sure of my reasoning for this question. I thought B would be the weakest base, since it is most stabilized due to the presence of resonance, induction, and the negative charge being on N. However, structure B has resonance, in addition to the negative being on the more electronegative oxygen. Ranking of bases in organic molecules from strongest to weakest.png
Hi Sorry for late reply
Just saw this post.
Order is D B A C
First Go with Atom
O is more EN than N so it is less basic than N .It means D is least basic as O is holding its LP tightly.
Then B because it has so many EN atoms (3 Cl) on it.
C is most basic because O is EDG here and making ring electron rich so deloaclization of LPs of N atom rons is less.