In which of the following the hydration energy is higher than the lattice energy?

For a salt to be highly soluble in water, its hydration energy must exceed its lattice energy. In the alkaline earth metal sulphates, the lattice energy remains relatively constant because the sulphate ion is very large. However, the hydration energy decreases significantly as the cation size increases (${\text{Mg}}^{2+}>{\text{Ca}}^{2+}>{\text{Sr}}^{2+}>{\text{Ba}}^{2+}$). Therefore, ${\text{MgSO}}_4$ has the highest hydration energy, making it the most soluble.