The intermolecular potential energy for the molecules A, B, C and D given below suggests that :

Know your College Admission Chances Based on your Rank/Percentile, Category and Home State.
Get your JEE Main Personalised Report with Top Predicted Colleges in JoSA
Bond enthalpy of AB bond is highest so A-B bond is more strong and B is highest electronegative atom. Order of bond length ⇒ A–A < A–B < A–C < A–D