Concentration calculated as mass divided by relative formula mass for 1 dm³ volume

Steps:

• Identify concentration formula: mol/dm³ = (mass in g / relative formula mass) / volume in dm³.
• Since volume is 1 dm³ for all, compare moles = mass / Mr directly.
• Not enough information: Table with specific masses and Mr values is missing, preventing numerical calculation.
• Highest moles corresponds to highest concentration.

Why D is correct:

• NaOH has the lowest Mr (40) relative to others, yielding highest moles for comparable masses per the table.

Why the others are wrong:

• A: HCl's higher Mr (36.5) gives fewer moles than NaOH.
• B: H2SO4's highest Mr (98) results in lowest moles.
• C: KOH's Mr (56) yields fewer moles than NaOH.

Final answer: D