(N/A) The solubility of sulphates of group $2$ elements depends on the balance between their hydration enthalpy and lattice enthalpy.
As we move down the group,the size of the metal cation increases,which leads to a significant decrease in the hydration enthalpy.
The lattice energy of these sulphates remains relatively constant.
For $BeSO_4$ and $MgSO_4$,the hydration enthalpy is very high,which is sufficient to overcome the lattice enthalpy,making them readily soluble in water.
In contrast,for $CaSO_4, SrSO_4$ and $BaSO_4$,the hydration enthalpy is not high enough to overcome the lattice enthalpy,resulting in their insolubility in water.