Most acidic hydrogen is present in:
The correct option is
B
Acidic hydrogen means it has a tendency to be released as H+ion. So, if any H-atom is attached to another atom or group of atoms with higher electronegativity, that H-atom can be released very easily as H+ion.
In option B, the hydrogens marked with red color are acidic hydrogens, due to the presence of hydrogens in between electron-withdrawing groups.