Which of the two structures (A) and (B) given below is more stabilised by resonance. Explain

CH3COOH  and CH3COOΘ        A                       B

Hint: Draw the resonance structures of compounds
 
Explanation:
 
Step 1:
 Resonating structures of (A) and (B) are as follows
(A) 
(B) 
 
Step 2: Structure (II) is less stable than structure (I) because later carries separation of positive and negative charges. Therefore, contribution of structure (II) is less than that of (I) towards the resonance hybrid of compound (A), i.e., CH3COOH. On contrary, structure (III) and (IV) are of equal energy and hence contribute equally towards the resonance hybrid of compound (B). Therefore, structure (B) is more stable than structure (A) i.e., CH3COO.