निम्नलिखित में से कौन सा यौगिक सबसे अधिक अम्लीय है?

Electron-withdrawing \( -NO_2 \) groups stabilize the phenoxide ion through -M and -I effects. 2,4,6-trinitrophenol (picric acid) has three \( -NO_2 \) groups at ortho and para positions, making it exceptionally acidic.