\(\mathrm{Li}^{\dagger}<\mathrm{Na}^{+}<\mathrm{Cs}^{+}\)

and the order of the size of given anions is

\(\mathrm{I^-}>\mathrm{F^-}\)

Thus, when the cation is largest and anion is smallest the cation to anion size ratio is maximum. Hence cation to anion size ratio is maximum