Which of the following compounds is the most acidic (i.e., has the lowest pK _ a value)?

Step-by-step solution

The acidic strength of substituted benzoic acids depends on the stability of their conjugate base (carboxylate anion). Electron-withdrawing groups (EWG) stabilize the carboxylate anion by dispersing the negative charge, thereby increasing the acidity. Conversely, electron-donating groups (EDG) destabilize the anion by intensifying the negative charge, which decreases the acidity. Let us analyze the substituents present at the para position in the given options: (A) Benzoic acid: No substituent. (B) p-Nitrobenzoic a