The four species above have the same electron configuration, 1s$^2$ 2s$^2$ 2p$^6$ 3s$^2$3p$^6$. Which of the following statements correctly identifies the species with the largest radius and provides an explanation based on Coulomb's law?
A. Cl$^-$, because its nuclear charge exerts the least attractive force on the electrons in the 3p sublevel.
B. Ar, because it is a neutral atom and the net force on the electrons in the 3p sublevel is zero.
C. K$^+$, because the loss of an electron results in a smaller attractive force between the nucleus and the electrons in the 3p sublevel.
D. Ca$^{2+}$, because the large positive charge on a cation causes increased repulsion among the electrons in the 3p sublevel.