Solubility of the alkali metal fluorides in water increases from LiF to CsF. The best explanation is that

1. Athe hydration enthalpy of the cation rises faster than the lattice enthalpy from Li to Cs
2. Bthe ionisation enthalpy of the metal decreases from Li to Cs
3. Cfrom Li to Cs the lattice enthalpy of the fluoride falls faster than the hydration enthalpy of the cation, so $\Delta H_{\mathrm{sol}}$ becomes more favourable
4. Dthe fluoride ion is more polarisable with large cations, which increases lattice enthalpy