The ions $O^{2-}, F^{-}, Na^{+}, Mg^{2+}$ and $Al^{3+}$ are isoelectronic. Their ionic radii show

• A
  an increase from $O^{2-}$ to $F^{-}$ and then decrease from $Na^{+}$ to $Al^{3+}$
• B
  a decrease from $O^{2-}$ to $F^{-}$ and then increase from $Na^{+}$ to $Al^{3+}$
• C
  a significant increase from $O^{2-}$ to $Al^{3+}$
• D
  a significant decrease from $O^{2-}$ to $Al^{3+}$