Solution:
The larger charge (=charge/size) of the cation produces larger polarization of electronic cloud of the anion and hence larger covalent character to the bond between cation and anion.
Among the following maximum covalent character is shown by the compound
The larger charge (=charge/size) of the cation produces larger polarization of electronic cloud of the anion and hence larger covalent character to the bond between cation and anion.