When  $\mathrm{NaF}, \mathrm{MgO}, \mathrm{KCl}$ and $\mathrm{CaS}$ listed in order of increasing lattice energy, which order is correct?

For compounds containing ions of same charge lattice energy increases as the size of ions decreases. Thus $\mathrm{NaF}$ has highest lattice energy. Arrange $\mathrm{KCl}, \mathrm{NaF}, \mathrm{CaS}$and $\mathrm{MgO}$ in increasing order of their lattice energies.

Thus, option D is correct.