Which type of bonding exists in $Li_2O$ and $CaF_2$ respectively?

Assertion $(A)$: Higher lattice enthalpy leads to greater stability of ionic compounds.
Reason $(R)$: Lattice enthalpy is a direct measure of the electrostatic forces of repulsion among the constituent ions in an ionic solid.
The correct answer is

The electronic configurations of four elements $L$,$P$,$Q$,and $R$ are given as: $L (1s^2, 2s^2 2p^4)$; $Q (1s^2, 2s^2 2p^6, 3s^2 3p^5)$; $P (1s^2, 2s^2 2p^6, 3s^1)$; $R (1s^2, 2s^2 2p^6, 3s^2)$. The formulas of the ionic compounds that can be formed between these elements are:

Sodium chloride easily dissolves in water. This is because

Lattice energy of an ionic compound depends upon

Which pair will form the most stable ionic bond?