Among the sulfates of alkaline earth metals, the solubilities of ${\mathrm{BeSO}}_4$ and ${\mathrm{MgSO}}_4$ in water, respectively are

• Down the group size of alkaline earth metal increases. 
• As the size increases hydration energy decreases
• As hydration energy decreases the solubility of sulphates decreases

So the solubility order of alkaline earth metal sulphates is 

${\mathrm{BeSO}}_4>{\mathrm{MgSO}}_4>{\mathrm{CaSO}}_4>{\mathrm{SrSO}}_4>{\mathrm{BaSO}}_4$.

The solubility of both ${\mathrm{BeSO}}_4$ and ${\mathrm{MgSO}}_4$ are high only but when compared to ${\mathrm{BeSO}}_4$, ${\mathrm{MgSO}}_4$ is slightly less soluble.   

Hence the correct option is (A).