The radius of (Atomic number of La = 57) is 1.06 A. Which one of the following given values will be closest to the radius of Lu$^{3+}$? Note: Atomic radius of Lu = 71.

Question

$\begin{array}{1 1}(a)\;Cr^{+3},Fe^{+3}&(b)\;Fe^{+3},Mn^{+2}\\(c)\;Fe^{+3},CO^{+3}&(d)\;Sc^{+3},Cr^{+3}\end{array}$