Identify the correct order in which the ionic radius of the following ions increases. $(I) \;F^{-};\;(II)\;Na^{+};\;(III) \;Na^{3-}$

$(a)\;I,II,III \\(b)\;I,II,III \\ (c)\;II,III,I \\ (d)\;II,I,III$

The correct order is : $Na^{+},F^{-},Na^{3-}$
$II,I,III$ is correct
Hence c is the correct answer.