The ionic radius of $Rb^{+}$ and $I^{-}$ respectively is $1.46 \ \mathring{A}$ and $2.16 \ \mathring{A}$. The geometry of $RbI$ would be similar to

• A
  $CsCl$
• B
  $NaCl$
• C
  $ZnS$
• D
  Boron-oxide