Among the following the strongest acid is

Step-by-step solution

K_a: 6.3 10⁻⁵ 3.3 10⁻⁵ 8.2 10⁻⁵ 1.75 10⁻⁵ - OCH ₃ group displays electron withdrawing acid strengthening inductive effect at the meta position but at the para position, an electron releasing acid weakening resonance effect operates (which at this position outweighs the inductive effect).