Among the following which compound will show the highest lattice energy?

For compounds containing cations of same charge.
lattice energy increases as the size of the cation decreases. Thus, NaF has highest lattice energy. The size of cations is in the order ${\mathrm{Na}}^{+}<{\mathrm{K}}^{+}<{\mathrm{Rb}}^{+}<{\mathrm{Cs}}^{+}$