Zere, \(Z\) is atomic number
\(\begin{array}{c|c|c}\hline \text { Species } & Z & \text { Electrons } \\\hline \mathrm{C}^{-} & 17 & 18 \\\mathrm{Ca}^{2+} & 20 & 18 \\\mathrm{K}^{+} & 19 & 18 \\\mathrm{S}^{2-} & 16 & 18 \\\hline\end{array}\)
Thus, ionic size is in order \(\mathrm{Ca}^{2+}<\mathrm{K}^{+}<\mathrm{C}^{-}<\mathrm{S}^{2}\)