`BeSO_4` is soluble in water but `BaSO_4` is insoluble because
A. `BeSO_4` is ionic while `BaSO_4` is covalent
B. `BeSO_4` is crystalline while `BaSO_4` is amorphous
C. `BeSO_4` has smaller lattice energy and high heat of hydration as compared to `BaSO_4`
D. `BeSO_4` is ionic while `BaSO_4` is covalent