Ambiguous total volume prevents exact calculation Steps:

• Moles of NaOH = mass / molar mass = 15 g / 40 g/mol = 0.375 mol.
• NaOH dissolved in 250 cm³ water in a graduated flask, but total solution volume not specified (could exceed 250 cm³ if flask larger).
• Without total volume, NaOH concentration cannot be found.
• Moles of NaOH in 25 cm³ sample unknown, so volume of 0.50 mol/dm³ HCl for 1:1 neutralization undetermined.

Why B is correct:

• Not enough information to confirm any option, including B.

Why the others are wrong:

• A: Not enough information.
• C: Not enough information.
• D: Not enough information.

Final answer: Not enough information.