0652/11 Physical Science Oct Nov 2016 Online Test | Cambridge IGCSE MCQ

Some reactions of sulfuric acid are shown.
${H_2}S{O_4} + 2KHC{O_3} \to {K_2}S{O_4} + 2{H_2}O + 2C{O_2}$
${H_2}S{O_4} + 2KOH \to {K_2}S{O_4} + 2{H_2}O{\rm{ }}$
${H_2}S{O_4} + MgC{O_3} \to MgS{O_4} + {H_2}O + C{O_2}{\rm{ }}$
${H_2}S{O_4} + MgO \to MgS{O_4} + {H_2}O{\rm{ }}$
Which compound gives the greatest mass of water when 10 g of it reacts with an excess of sulfuric acid?
$\left[ {{M_r}:MgO,{\rm{ }}40;MgC{O_3},84;KOH,56;KHC{O_3},100} \right]$