Option (A) is correct. Isoelectronic species such as $F^-$, $Ne$ and $Na^+$ contain the same number of electrons. Their radii differ because of their different nuclear charges. The cation with the greater positive charge will have a smaller radius because of the greater attraction of the electrons to the nucleus, whereas an anion with a greater negative charge will have a larger radius due to increased electron-electron repulsion outweighing the nuclear charge.