The conic radii of $Rb^+$ and $I^-$ are $1.46\;A^{\circ}$ and $2.16\;A^{\circ}$ respectively . The most probable type of structure exhibited by it is

Question

$\begin{array}{1 1} \text{Nacl type } \\ \text{Zns type } \\ \text{Cscl type } \\ \text{$CaF_2$ type } \end{array}$