Which of the following alkaline earth metal sulphates has hydration enthalpy higher than the lattice enthalpy?

For a substance to be soluble, hydration enthalpy must be greater than or equal to lattice enthalpy. Solubility of alkaline earth metal sulphates decreases down the group. ${\text{BeSO}}_4$ and ${\text{MgSO}}_4$ are readily soluble because the high hydration enthalpy of the small ${\text{Be}}^{2+}$ and ${\text{Mg}}^{2+}$ ions outweighs the lattice enthalpy.