The correct increasing order of the ionic radii is

For isoelectronic species, as nuclear charge increases radius decreases. Greater the positive charge, the lesser the size of the ion. Greater the negative charge, the larger the size of an ion.

$$\begin{gathered} {\mathrm{Ca}}^{2+}< {\mathrm{K}}^{+} < {\mathrm{Cl}}^{-} < {\mathrm{S}}^{2-} \\ \mathrm{p} 20 19 17 16 \\ \mathrm{e} 18 18 18 18 \end{gathered}$$

So, the correct option is (D).