Identify the sets containing isostructural molecules from the following
I. \(\text{SiF}_4\), \(\text{SF}_4\)
II. \(\text{IO}_3^-\), \(\text{XeO}_3\)
III. \(\text{BH}_4^-\), \(\text{NH}_4^+\)
IV, \(\text{PF}_6^-\), \(\text{SF}_6\)
The correct option is