The correct arrangement for the ions in the increasing order of their radius is :

Since, Ca²⁺, K⁺, S^2- have same number of electrons so, they are isoelectronic ions, as we know that the ion having  greater number of protons will be smallest in size. Thus, the increasing order of ionic radii is ${\mathrm{Ca}}^{2+}<{\mathrm{K}}^{+}<{\mathrm{S}}^{2-}$.