Concept:The neutralization reaction between H2SO4 and NaOH has a mole ratio of 1:2.Explanation:Moles of NaOH=0.1moldm−3×0.025dm3=0.0025mol.From H2SO4+2NaOH→Na2SO4+2H2O, moles of H2SO4 neutralized =20.0025=0.00125mol.Volume of H2SO4=0.50.00125=0.0025dm3=2.5cm3.Answer:2.5cm3, which is option B.