Among the following compounds the most acidic is

Step-by-step solution

Acidic nature ∝ electron withdrawing group - I , - R , ortho effect Acidic nature ∝ 1 e l e c t r o n r e l e a s i n g g r o u p + I , + R A carboxylic acid is more acidic than phenol due to more stability of conjugate base. Due to ortho effect o- hydroxyl benzoic acid is strongest acid here and correct order of decreasing of acidic nature is